Which is a requirement for natural selection to occur?
a. heritable variations for some traits
b. the ability of an organism to improve a trait during its lifetime
c. equal probability of survival for all offspring
d. fewer offspring than the environment can support

The right answer is A. heritable variations for some traits .

Natural selection per is simply a sort of the individuals most likely to survive or reproduce, regardless of the reason why they possess such an ability. To induce the evolution of a particular biological trait in a population under the effect of natural selection, this biological trait must vary from one individual to another, whether this individual variation is heritable, and that this variation correlated with that of reproductive success or the probability of survival of individuals.

2%? i tried finding the exact sorry if it's not 100% correct ; -;