What is the role of tropomyosin in muscle contraction?

Ihave a question. diplontic animals usually produce both eggs or sperm which are :

How does the fossil record provide evidence that the modern whale evolved from the anthracotheres? a) the modern whale looks like their ancestor the anthracotheres. b) the modern whale has all of the same structures as their ancestor. c) there is not enough evidence to suggest the the modern whale evolved from the anthracotheres. d) the anthracotheres has a structure that is still present in the modern whale, but is no longer of use to the modern whale.

What is the difference between hypothesis, theories, laws, and observations?