Why Do Some Invertebrates,such as Lobsters,show a "Stair-Step" Survivorship Curve

Why do some invertebrates,such as lobsters,show a "stair-step" survivorship curve?

A) Many invertebrate species mate and produce offspring on multiyear cycles.
B) Younger individual species have a higher survivorship than older individuals.
C) Invertebrates are vulnerable to predation during molting when their shell is soft.
D) Some species have fluctuating population cycles according to the frequency of sunspots.
E) The number of fertilized eggs that mature to adult females depends on ambient temperature.