Question

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

Explanation:

Natural selection depends on heritable trait variations: individuals with advantageous traits pass them to offspring, driving adaptation. The other options are incorrect: lifetime trait improvement is Lamarckian (not natural selection's basis), equal survival probability removes selection pressure, and natural selection requires more offspring than the environment can support (overproduction) to create competition.

Answer:

heritable variations for some traits