If an organism has 6 haploid chromosomes, how many chromosomes are present? 6 12

What are genotypes? what are phenotypes?

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.