Which of the following is a true statement? a. mammals were the prominent species just before the extinction of dinosaurs. b. massive extinction of species results in less species diversity but is followed by an explosive diversification of certain remaining species. c. as dinosaurs became extinct, reptiles remained as their sole descendants. d. pangaea started to break up to form geographic isolation for many species about 65 million years ago.

The correct answer is B.

Explanation:

Option A is wrong. Mammals were not the prominent species before the extinction of dinosaurs because the mammal species that lived during the dinosaurs' era were so small that they only weighed several grams and occupied small areas as their habitats.

Option C is wrong. As dinosaurs became extinct, reptiles and "birds" remained as their descendant which evolved to some of the species that we know today.

Option D is wrong. Pangea started to break up to form the geographic isolation for the diversion of many species around 175 million years ago.

So the correct answer is B. Massive extinction disrupts and changes the food chain in such a big way that it triggers a domino effect that leads to species adapting to their new environment and diversifying thus forming new species in the process.

I hope this answer helps.