Answer:
A
Explanation:
"A red dwarf, which is half as massive as the sun, can last 80 to 100 billion years, which is far longer than the universe's age of 13.8 billion years. (This long lifetime is one reason red dwarfs are considered to be good sources for planets hosting life, because they are stable for such a long time.)"
Forests and other green plants uses carbon dioxide in photosynthesis thus lowering its amount in the atmosphere. In assumption, we can claim that in the ice ages, the low level temperatures may have caused the carbon dioxide levels to neutralize over these phenomenons, also to note that there were less oxygen-breathing organisms and higher carbon-dioxide dependent performing photosynthesis.
Cyclins and cyclin-dependent kinases are responsible for the progress of the cell through the various checkpoints.
The answer is plants. Plants are at the start of the food chain :)
Answer:
Oxygen
Explanation:
The formula for cellular respiration is oxygen + glucose -> water, carbon dioxide, energy. You can already cross out A and D because they aren't in the formula, so you have two left, water and oxygen. The reason why it is oxygen and not water is because without oxygen you can't even have water. also, I just got this right on my test :-)
