In a gene that normally contains three exons, which of the following changes probably will NOT activate the nonsense-mediated mRNA decay pathway? The sizes of exons 1 to 3 are 100, 150, and 200 nucleotide pairs, respectively.

A) A nonsense mutation in exon 1.
B) A nonsense mutation in exon 2.
C) A mutation in the first intron resulting in the inclusion of a large intronic fragment in the mature mRNA.
D) A frameshift mutation in exon 1.
E) A mutation in exon 2 leading to its loss through exon skipping.