Answer:
B
Explanation:
The Earth is tilted 23.5 degrees on its vertical axis. During the northern hemisphere's spring and summer, the northern hemisphere is tilted towards the Sun.
I would say d. Multi-part protein that reversibly binds to oxygen molecules (...)
Answer:
A
Explanation:
Today, the atmosphere holds about 21 per cent oxygen. ... When the first simple organisms appeared in the oceans more than 3.5 billion years ago, the atmosphere was mostly nitrogen, hydrogen, water vapor, and carbon dioxide
