The right answer is B.
The answer B is the only proposition which specified at which stage the event must occur, in fact, the meiosis.
Meiosis is a characteristic division of reproductive cells that can generate gametes to form new species (desendence). So if a mutation occurs at this time (such as recombinations) it will inevitably be inherited.
a) ribosomes on the rough endoplasmic reticulum
mRNA (created by DNA) leaves the nucleus through the nucleic pores, and from there will enter a nearby ribosome since the rough endoplasmic reticulum is surrounding the nucleus. It is there that polypeptides are made and transported in vesicles to the Golgi apparatus because they cannot touch the cytoplasm when still incomplete. Hope this helped.