Answer: isotopes is the answer to this question
A membrane bound nucleus (or just a nucleus in general)
Your answer is B
When the F1 generation exhibits both the parental characters, this is called codominance. The offspring will be a combination of both the parent. The ABO blood group system is one of the best examples of codominance. There are different types of red blood cells such as A, B, AB and O with or without the Rh factor.
Sure hope this helps
Your answer is (B.)
Fossils in newer layers if rock are generally estimated to be younger than fossils found in the deeper layers because it is closest to the surface. The soil and earth didn't have enough time to "bury" the remains of the dead animal ( Bury is used for a simpler term) underground. The farther down a fossil is the more likely it is older unless the animal tends to burrow. Seeing as the question is probably talking of older animals that is unlikely for an animal to burrow that far. So your answer is B.