B. imagine a catastrophic event, such as a volcano, hypothesize what will happen to these photosynthetic organisms and their impact on food chains and food webs.

answer; /// the correct )

true, i don't really know what you're asking but from the info you provided im guessing the answer is true.

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.