If a single base pair gets damaged and goes missing from an rna, what would most likely happen?

A frame-shift mutation would occur. This is because a deletion will cause a change in codon sequence from the point of mutation to the end of the mRNA.  If the mutation is closer to the start of the mRNA, the larger the effect of the mutation on the translated protein.

c

explanation:

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).