Researchers Used the CRISPR System to Make 455 Different Cuts

Researchers used the CRISPR system to make 455 different cuts in the porcine endogenous retrovirus (PERV) pol genes in the pig genome.All of the PERV genes were inactivated in the pig embryos even though only 20 percent of the resulting mutations were larger than nine base pairs.The resulting mutations were successful at knocking out the PERV genes because

A) even single point mutations can be enough to make a gene product useless or inactivate a gene.
B) large mutations are not useful in knocking out genes.
C) inactivating 20 percent of the PERV genes is just as good as inactivating 100 percent of the PERV genes.
D) only 20 percent of the PERV genes need to be inactivated to result in all of them being inactive.