What is when it's why because it's what as it's where so it's who.?

What is thought to have caused the mass extinction at the end of the cretaceous period?

Chloroplasts and bacteria are in size. a. similar b. at different ends of the size range c. exactly the same d. none of these

In order to study genetic mutations, scientists must study genetic material. which statement describes the genetic material scientists are most likely studying? a) they study alleles that contain chromosomes, which are rna.b) they study alleles that contain genes, which are chromosomes.c) they study chromosomes that contain genes, which are dna segments.