Answer: The correct answer is -
A.duplication.
Duplication can be described as a type of mutation that occurs when a portion of DNA sequence or a chromosome is duplicated, resulting in mutiple copy of that region. Duplication can result from misaligned homologous chromosomes, which undergo unequal crossing-over during meiosis.
In the given sequence-
GCTTAGCGC → GCTTATAGCGC
TA nucleotide sequence in the original DNA is duplicated, resulting in another TA sequence in the mutated DNA.
Thus, option A) is the right answer.