SolveItNCERT · CBSE Boards

NCERT Exemplar · Class 9 Science Natural Resources

56 questions · 56 still being checked

Multiple Choice Questions 1–10 (part 1 of 6)

  1. Exercise 1

    The atmosphere of the earth is heated by radiations which are mainly
    (a)
    radiated by the sun
    (b)
    re-radiated by land
    (c)
    re-radiated by water
    (d)
    re-radiated by land and water

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (d)
    (d) Re-radiated by land and water.\[\text{sun's rays} \rightarrow \text{land, water (absorb)} \rightarrow \text{re-radiated as heat} \rightarrow \text{atmosphere heats} \]The atmosphere is largely transparent to incoming sunlight; it warms mainly from the long-wave heat the land and water surfaces send back.

  2. Exercise 2

    If there were no atmosphere around the earth, the temperature of the earth will
    (a)
    increase
    (b)
    go on decreasing
    (c)
    increase during day and decrease during night
    (d)
    be unaffected

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (c)
    (c) Increase during day and decrease during night.\[\text{no atmosphere} \Rightarrow \text{no filtering by day, no blanket by night} \Rightarrow T\uparrow\ (\text{day}),\ T\downarrow\ (\text{night}) \]Like the moon, with no air to moderate it, surface temperature would swing to extremes each day-night cycle.

  3. Exercise 3

    What would happen, if all the oxygen present in the environment is
    converted to ozone?
    (a)
    We will be protected more
    (b)
    It will become poisonous and kill living forms
    (c)
    Ozone is not stable, hence it will be toxic
    (d)
    It will help harmful sun radiations to reach earth and damage many
    life forms.

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (b)
    (b) It will become poisonous and kill living forms.\[\text{O}_2 \rightarrow \text{O}_3\ (\text{all}) \;\Rightarrow\; \text{no O}_2\text{ for respiration; O}_3\text{ is toxic to breathe} \]Organisms need molecular oxygen to respire; losing it entirely to a toxic gas would be fatal, not protective.

  4. Exercise 4

    One of the following factors does not lead to soil formation in nature
    (a)
    the sun
    (b)
    water
    (c)
    wind
    (d)
    polythene bags

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (d)
    (d) Polythene bags.Sun, water and wind physically and chemically weather rock into soil over time; polythene is inert and non-biodegradable, contributing nothing to that process.

  5. Exercise 5

    The two forms of oxygen found in the atmosphere are
    (a)
    water and ozone
    (b)
    water and oxygen
    (c)
    ozone and oxygen
    (d)
    water and carbon-dioxide

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (c)
    (c) Ozone and oxygen.Atmospheric oxygen exists mainly as diatomic \(\displaystyle \text{O}_2\), used in respiration, and as ozone, \(\displaystyle \text{O}_3\), concentrated in the stratosphere where it absorbs ultraviolet radiation.

  6. Exercise 6

    The process of nitrogen-fixation by bacteria does not take place in the presence of
    (a)
    molecular form of hydrogen
    (b)
    elemental form of oxygen
    (c)
    water
    (d)
    elemental form of nitrogen

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (b)
    (b) Elemental form of oxygen.\[\text{O}_2\text{ present} \;\Rightarrow\; \text{nitrogenase inhibited} \;\Rightarrow\; \text{N}_2\text{-fixation blocked} \]The bacterial enzyme nitrogenase that reduces atmospheric nitrogen is oxygen-sensitive, so fixation proceeds only under low-oxygen conditions.

  7. Exercise 7

    Rainfall patterns depend on
    (a)
    the underground water table
    (b)
    the number of water bodies in an area
    (c)
    the density pattern of human population in an area
    (d)
    the prevailing season in an area

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (b)
    (b) The number of water bodies in an area.Rainfall depends on the moisture available to form clouds; more lakes, rivers and seas nearby mean more evaporation, feeding local cloud formation and precipitation.

  8. Exercise 8

    Among the given options, which one is not correct for the use of large
    amount of fertilisers and pesticides?
    (a)
    They are eco-friendly
    (b)
    They turn the fields barren after some time
    (c)
    They adversally affect the useful component from the soil
    (d)
    They destroy the soil fertility

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (a)
    (a) They are eco-friendly.Heavy fertiliser and pesticide use strips useful soil components, leaves fields barren and destroys fertility over time — none of that is eco-friendly, the false claim here.

  9. Exercise 9

    The nitrogen molecules present in air can be converted into nitrates and
    nitrites by
    (a)
    a biological process of nitrogen fixing bacteria present in soil
    (b)
    a biological process of carbon fixing factor present in soil
    (c)
    any of the industries manufacturing nitrogenous compounds
    (d)
    the plants used as cereal crops in field

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (a)
    (a) A biological process of nitrogen-fixing bacteria present in soil.\[\text{N}_2\ (\text{air}) \xrightarrow{\text{nitrogen-fixing bacteria in soil}} \text{NO}_3^-,\ \text{NO}_2^- \]Bacteria such as Rhizobium in root nodules convert atmospheric nitrogen into nitrates and nitrites usable by plants.

  10. Exercise 10

    One of the following processes is not a step involved in the water-cycle
    operating in nature
    (a)
    evaporation
    (b)
    transpiration
    (c)
    precipitation
    (d)
    photosynthesis

    Matches the book, not yet reviewed

    This working reaches the answer NCERT prints. It has not yet been read through by hand.

    NCERT’s answer
    (d)
    (d) Photosynthesis.Evaporation, transpiration and precipitation move water between land, plants, air and clouds in the water cycle; photosynthesis uses water but is not one of its transport steps.