Not sure what all these answers are ?? please help ???!

Which of the following will not cause mass extinction? a. drastic change is weather b. geological change c. both a and b d. none of the above

Which is an example of a population?

Legumes, a type of plant, require rhizobia, a type of soil bacteria, to survive since these organisms fix nitrogen during photosynthesis. rhizobia use the legumes for food. what would most likely happen to the legume population if rhizobia suddenly became extinct?