Question

1. during rusting, iron reacts with oxygen to form

a iron (iii) oxide
b iron (iv) oxide
c iron (v) oxide
d iron (vi) oxide

1. members of the same species living at the same place at the same time make a/an

a population
b ecosystem
c community
d trophic level

1. the westerlies are winds that blow

a from the poles
b towards the poles
c towards the equator
d from the equator

1. the p - n junction diode has

a equal number of holes and electrons
b no holes
c no electrons
d more electrons than holes

1. the correct sequence of the arrangement of vertebrae in a mammal is

a thoracic, lumbar, cervical, caudal
b cervical, caudal, lumbar, thoracic
c thoracic, cervical, lumbar, caudal
d cervical, thoracic, lumbar, caudal

1. which of the following structures is present in animal cells only?

a mitochondrion
b lysosomes
c golgi body
d ribosome

1. loss of appetite and poor growth in humans are due to the deficiency of

a sodium
b iodine
c copper
d zinc

1. nucleons refer to the sum of

a electrons and neutrons in an atom.
b protons and neutrons in an atom.
c protons and electrons in an atom.
d electrons and molecules in an atom.

1. which of the following statements are correct?

i. green house effect can be reduced by afforestation.
ii. one effect of ozone layer depletion is global warming.
iii. green house effect is reduced by bush burning.
a ii and iii only
b i and iii only
c i and ii only
d i, ii and iii

Explanation:

1. Iron reacts with oxygen to form iron(III) oxide, which is a common oxidation product of iron.
2. Members of the same species living at the same place at the same time make a population. A community is made up of different species. A trophic - level refers to a position in a food chain.
3. Westerlies are winds that blow from the subtropical high - pressure belts towards the poles.
4. In a P - N junction diode, there are more holes in the P - region and more electrons in the N - region, but not equal numbers of holes and electrons.
5. The correct sequence of vertebrae in a mammal is cervical, thoracic, lumbar, caudal.
6. Lysosomes are present in animal cells only. Mitochondria, Golgi body and ribosomes are present in both plant and animal cells.
7. Loss of appetite and poor growth in humans are due to the deficiency of zinc.
8. Nucleons refer to the sum of protons and neutrons in an atom.
9. Afforestation can reduce the greenhouse effect as plants absorb carbon dioxide. Ozone layer depletion is not the same as global warming. Bush burning releases carbon dioxide and other greenhouse gases, increasing the greenhouse effect. So only statement I is correct.

Answer:

1. A
2. A
3. A
4. D
5. D
6. B
7. D
8. B
9. C