Which best summarizes the concept of natural selection?
a. nature selects the organisms with the most mutations.
b. the fittest organisms are selected for.
c. an organism will always mutate to survive.
d. mutations make organisms more fit?

Correct B). The fittest organisms are selected for.

The theory of Natural selection is given by Charles Darwin, according to it,  the natural selection is the process in which the organism that is more suited are selected by the natural selection and they are most likely to survive and reproduce in order to pass these traits to the next generation.

The organism with the highest survival and reproduction will be those whose genes best represented in the next generation. Natural selection occurs to cause evolution and select the fittest.

b. the fittest organisms are selected for.

Explanation:

Natural selection is nothing more than an evolutionary mechanism that is based on the survival and differential reproduction of individuals in a population. It is often said that natural selection selects the most fit organism to live in a given environment. For this reason, we can say that among the options given in the question above, the one that best summarizes the concept of natural selection is "the fittest organisms are selected for".