In an Organism Such as a Sea Urchin, Administration of Actinomycin

In an organism such as a sea urchin, administration of actinomycin D prevents all mRNA synthesis. However, early development up to gastrula formation can take place in the presence of actinomycin D but gastrulation cannot. This implies that _________.

A) actinomycin D is part of the normal environment of a sea urchin and serves as a developmental signal molecule
B) maternal effect genes regulate development until gastrulation
C) mRNA synthesis is not required after gastrulation
D) development beyond gastrulation requires actinomycin D
E) immature sea urchin embryos produce actinomycin D to regulate further development