Unequal reproductive success .Group of answer choicescan lead to a population being less well adapted to its environmentcan lead to natural selectionalways decreases the size of a populationdoes not affect the frequency of expression of traits in succeeding generations of a populationincreases variation

can lead to natural selection

Explanation:

This is because if there is unequal reproductive success then one of the organisms is better suited for reproducing, surviving, and passing down their genes to their offspring rather than the organism who is unfit. This is where natural selection comes into play because natural selection is process where individuals better suited for their environment produce more and have better survivality.

So overtime, the organism which is weaker  (in sense of fitness) (here fitness relates to reproduction and survival), will not pass as many genes and won't survive, whereas, individual better suited will, hence in  a way "Nature selected" the better fit organism.