Because they alter the reading frame of all base-pair triplets, base-pair additions and deletions are collectively referred to as:
a. inversions
b. transversions
c. framshift mutations
d. point mutations
e. codon mutations

The correct answer is option c. "frameshift mutations".

Explanation:

The reading frame of a gene is based on base-pair triplets, starting from the start codon until the ribosome encounters with the end codon. Base-pair additions and deletions are collectively referred to as frameshift mutations because they alter the reading frame of the gene. Base-pair additions and deletions break down the original sequence of the gene triplets, which alters the open reading frame and usually results in the production of non active proteins.