What Hypothesis Were the Scientists Testing

What hypothesis were the scientists testing?

A) That some sea slug genes were present in chloroplast chromosomes
B) That chloroplasts can function without some proteins involved in photosynthesis
C) That the sea slugs have to continuously consume chloroplasts to replace the older ones
D) That some chloroplast genes were present in the sea slug chromosomes
E) That only photosystem II is necessary for photosynthesis