Answer:
The correct answer would be D) mutations involved the genetic variation of the bugs are random.
Mutation is defined as a permanent change in the nucleotide sequence of a genome in an organism.
Mutation can be randomly caused by DNA replication errors, exposure to carcinogenic materials or radiations, transposons et cetera. It can sometimes occur spontaneously which are termed as a spontaneous mutation.
Mutation does not always result in loss of function. It may also result in a gain of function such as resistance to any chemical.
Similarly, in bed bugs the mutations which allow their survival against chemical pesticides are random.