Many paleontologists hypothesize that present-day whales evolved from ancient ancestors that had four legs and walked on land. Evidence for that hypothesis would be a sequence of whale-like fossils
A. in which the oldest fossils had flipperlike appendages and the most recent fossil had four limbs.
B. in which the oldest fossil had four limbs and the most recent fossil had flipperlike appendages.
C. that indicate that the ancestors of present-day whales were wiped out during a mass extinction.
D. that indicate that whales evolved before animals with four legs.

B

Explanation:

If the oldest fossils showed legs and the more recent ones had only flippers, it would show the change over time.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!