2. In order to grow, animals with an exoskeleton must a. Shed their skin
b. shed their shells
C. continue cell reproduction
d. find larger shells to inhabit.

a.shed their skin..

Explanation:

Exoskeleton

A true exoskeleton, like that found in arthropods, must be shed (moulted) when it is outgrown. ... The new exoskeleton is still capable of growing to some degree, however. Animals of the order arthropoda, like lizards, amphibians, and many other animals that shed their skin, are indeterminate growers