What best describes biogeographoc isolation

Which of the following statements is true? a. the main cause for speciation is an increase in gene flow. b. organisms that reproduce asexually are not considered part of a species. c. on a tree of life diagram, speciation is shown by the merging of two different lineages. d. the size of the geographic area inhabited by a population can cause speciation.

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

The third stage of cellular respiration is (2 points)