Question

The level of oxygen in the form of O2 in the Earth's atmosphere ________________.

A. has not changed substantially in the past 450 million years
B. is drastically decreasing due to pollution
C. is no different than it was 4.6 billion years ago
D. is drastically increasing due to growth of new bacterial strains
E. cannot change because Earth is a closed system

Answer 1

The level of oxygen in the form of O2 in the Earth's atmosphere has not changed substantially in the past 450 million years. The composition of the Earth's atmosphere has changed over time, but the level of oxygen has remained relatively stable. The burning of fossil fuels has resulted in an increase in carbon dioxide levels. The correct option is A.

Step-by-step explanation:

The level of oxygen in the form of O2 in the Earth's atmosphere has not changed substantially in the past 450 million years.

Several lines of evidence, including studies of ancient rocks and the chemistry of minerals, show that the composition of the Earth's atmosphere has changed over time, but the level of oxygen has remained relatively stable over the past millions of years.

It is important to note that the burning of fossil fuels in recent history has resulted in a dramatic increase in carbon dioxide levels, which is a greenhouse gas and can contribute to climate change.

Hence, Option A is correct.