Answer: The correct answer is-
c. their hard exoskeleton cannot grow larger.
In arthropods, molting can be described as the process of shedding of external skeleton ( exoskeleton) so as to enable the organisms to grow.
Arthropods like grasshoppers possess hard exoskeleton ( present outside the body for protection) that can not be grown larger.
They undergo molting because their exoskeleton can not grow larger and therefore needs to shed periodically so that the body can grow larger.
Thus, in order to allow the organism to grow, the tough exoskeleton should be shed periodically and replaced by new, soft exoskeleton ( which becomes harder after some time).
