a grammer question

pegirl

--------,the cell bodies that control the heredity of an animal or a plant.

(A)In chromosomes the chief material in DNA
(B)DNA is the chief material in chromosomes
(C)The chief materail in chromosomes is DNA
(D)In chromosomes DNA is the chief material

why can't not choose C???could anyone explain why??
also what is B different from D ??

林君

独立来看，B和D并没有语义差别，但若要进入句子，只有前者符合要求，因为the　cell　bodies指的是chromosomes。一般来说，逗号之前必须是the　cell　bodies的所指。从这个角度来看，C也就不可能是答案了

ellenmoving

应选B, the cell bodies 指的是 chromosomes, 复数对复数.
如选C, the cell bodies 指的是 DNA, 复数对单数, 错.