Since animals have nerve and muscle tissue and plants do not, which of the following events in earth’s history would be associated with adaptive radiation of many groups of animals, and not particularly that of plants?
A. increase in atmospheric O2
B. great increase in land mass area
C. changes in global ocean temperatures
D. meteorite impacts and volcanic eruptions
E. earthquake activity causing increased barrier formation

The nerve cells and the muscle cells suggest that the the presence of oxygen in the atmosphere was an adaptive radiation which brought the existence of different animals. The conditions became favorable for different animals to survive on Earth only when the availability of oxygen improved in the atmosphere. As animal cells like the muscle cells require a constant supply of oxygen, we can hence say that increase in atmospheric oxygen was the adaptive radiation for supporting many group of animals.