The answer is C, it results in offspring with genetic variations.
Sexual reproduction is where a male gamete fuse with a female gamete to form a zygote, which is their offspring.
Gamete cells are different to the other somatic (body) cells in an organism, they have only half of the chromosomes. They are products of a kind of cell division called meiosis. They are also said to be haploid cells.
When 2 haploid cells fuse together, the number of chromosomes will add up so that it'll match the correct number of somatic cells of that organism. Because both gamete contains half of the chromosomes, when they fuse together, they produce offsprings with some characteristics from both parents.
The different characteristics from the parents and others are said to have genetic variation. They're different to others in some way, even they're still the same organism.
This can actually help that type of organism survive, for example if a huge disease breaks out, there may be still some organisms with a characteristic which can help them stay alive.