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

A)Many invertebrates mate and produce offspring on multiyear cycles.
B)Within a species of invertebrates, younger individuals have a higher survivorship than older individuals.
C)Many invertebrates moult in order to grow, and they are vulnerable to predation during their "soft shell" stage.
D)Many invertebrate species have population cycles that go up and down according to the frequency of sunspots.
E)The number of fertilized eggs that mature to become females in many species of invertebrates is based on ambient temperature.