Prelims 2018 · Q57
Consider the following statements:
- 1.The Earth's magnetic field has reversed every few hundred thousand years.
- 2.When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
- 3.When living organisms originated, they modified the early atmosphere of the Earth.
Which of the statements given above is/are correct?
- (a)1 only
- (b)2 and 3 only
- (c)1 and 3 only
- (d)1, 2 and 3
Show answer
UPSC's answer: (c)
NCERT answers it: Class 11 Fundamentals of Physical Geography, Ch 2 (The Origin and Evolution of the Earth); Class 11 Fundamentals of Physical Geography, Ch 4 (Distribution of Oceans and Continents).
Fundamentals of Physical Geography: the early atmosphere had very little free oxygen, and living things later changed it through photosynthesis (ch 2). The ocean floor shows strips of normal and reversed magnetism (ch 4). So 1 and 3: (c).
Hindi version: UPSC's official question paper (2018), question 57 ↗