The correct option is B Stadium
Instar is the shape and size of insect between two successive moultings.
Metamorphosis is the change from one form to the next in the life history of an organism.
The process of casting off old cuticle and deposition of new cuticle at certain time interval is known as ecdysis.
Stadium is the time interval between two moulting. The first stadium is the time between hatching and the first moult.
Thus, the correct answer is option B.