Two factors that drive natural selection are listed below.

1. percentage of young that survive
2. ability to produce offspring

which statement is true about the two factors?

factor 1 causes genetic variation and factor 2 causes differential reproductive success.
factor 1 causes differential reproductive success and factor 2 causes genetic variation.
both factors cause differential reproductive success.
both factors cause genetic variation.

Imagine a self-reactive t cell that has not undergone clonal deletion in the thymus (that is to say, it has escaped central tolerance). if it encounters self antigen in the absence of an infection or inflammation, what will happen to this self-reactive t cell? (select two answers) (a) the t cell undergoes clonal expansion. (b) the t cell gains effector functions. (c) the t cell undergoes apoptosis. (d) the t cell becomes activated. (e) the t cell becomes anergic.