One adaptation that is unique to marine mammals is they nurse their young.. The correct option among all the options that are given in the question is the fourth option or the last option or option "d". I hope that this is the answer that you were looking for and the answer has come to your desired help.
B.when the eye reaches the land mass
I think it is (b) i have studied this before. ( =
Explanation:
The experimenter alters the independent variable with the hopes of collecting data about how the dependent variable changes in response.Other variables have to be controlled so that any changes of the dependent variable are attributed to the known independent variable.