Similar bone structure found in distinct organisms indicates that A.
they live in the same habitat
B.
they fill the same niches
C.
they share a common ancestor
D.
All of the above

C

Explanation:

The similar bone arrangement of the human, bird, and whale forelimb is a structural homology. Structural homologies indicate a shared common ancestor. ... For example, the forelimbs of whales, humans, and birds look different on the outside because they're adapted to function in different environments.

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.