Bacteria are organisms that reproduce asexually. how is this better for them
than reproducing sexually?

a. they have more genetic variation within their population.
b. they produce more tetrads for reproduction.
c. they can grow to larger populations more quickly.
d. they use more cellular energy to reproduce.

C. They can grow to larger populations more quickly

Explanation:

Bacteria are the key entities of biogeochemical cycles (Nitrogen, Carbon, Oxygen, etc.) on Earth. The strength of these cycles is typically achieved when they can multiply faster in a relatively short time period. If all bacteria on Earth start reproducing via sexual means only, then many of the biogeochemical cycles would take forever, thus generating nutrients at a slower rate. Since higher organisms (e.g. eukaryotes) depend on the abundant supply of nutrients, the overall life on Earth would be compromised to a larger extent in the absence of sufficient nutrients supply. Thus, it is  beneficial for all forms of life that bacteria reproduce mainly via asexual means.

PS: A simple bacterium can produce millions of copies in 24 hours period.

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.