Correct Answer: (3) Organism X=unicellular; organism Y=simple multicellular

According to most theories on evolution, the initial organisms of the Earth were simple and then evolved to more complex organisms in order to cope up with the changing environments. Thus, all the other options are incorrect, except for option (3), wherein organism X is a unicellular organism that may be evolved into simple multicellular organism like organism Y.

Correct Answer: (1) It is more closely related to the mammoth that it is to the West African manatee.

All of the species stated here has a common original ancestor (not identified). From this common ancestor, two lines of ancestry where formed which further diverged due to evolution of new species. For the first line, mammoth and West African manatee evolved, however, the mammoth cam in an earlier time.

Incorrect Answers:

West Indian manatee, Brazilian manatee, and Stellar's sea cow evolved from the second line of ancestry, not from the first line where West African manatee evolved.

Correct Answer: (4) D

Organism D evolved from organism A. Organism D did not evolve into another species or continued to exist in the next time frame.

Incorrect Answers:

Organisms E and C lived in the time frame after the time frame of organism D. On the other hand, organism J lived after the time frame of organisms E and C.

Correct Answer: (2) B

After four time frames, organism B still existed. It have been evolved into organisms C and J, but the original kind still existed.

Incorrect Answers:

Organism A lived in three time frames but eventually became extinct at the 4^th time frame. Organisms C and A existed only in one time frame each.