Some single-celled organisms that make copies of themselves through mitosis. Which of the following best decribes the function of the cell cycle in such single-celled organisms?

a. reproduction

b. repair

c. growth

d. protection

A. reproduction

(Sounds like the most accurate answer given that they're asking about mitosis.)

Single celled organisms reproduce by making identical copies of themselves through asexual mode of reproduction.

Mitosis is a process of cell division where two cells identical to the first cell are formed. The two daughter cells are genetically identical produced by mitosis. The role of mitosis is different for different organisms.

For unicellular organisms the mitosis is a mode of asexual reproduction and produces identical copies from the single cell while in multicellular organisms produces more number of cells for growth and repair.

Here it is referring to making copies by mitosis so in such single celled organisms the best description would be a. reproduction.