Diatoms Have a Special Problem

Diatoms have a special problem:

A) because their + and - mating strains are nonmotile and have to be dispersed by currents
B) because their heavy siliceous shells impede conjugation
C) because they must await a chemical signal from a fish before they can become mobile and search for mating partners
D) because their two halves fit like the lid and body of a pillbox and on repeated cell divisions the half that is overlapped gets progressively smaller
E) because the gametes experience difficulty in exiting the overlapping halves of their siliceous shells