Answer:
c) It introduces a premature stop codon into the mRNA
Explanation:
Nonsense mutation is a type of point mutation (single nucleotide base is changed) which leads to premature stop codon. Stop codons are also called nonsense codons and that is way this type of mutation is called nonsense mutation. As a consequence, synthesized protein is incomplete and shorter than it should be (truncated protein), usually nonfunctional.