Dr. Hakuta's research among Hispanic children in the United States indicates that the more the children use both Spanish and English, their intellectual advantage is greater in skills underlying reading ability and nonverbal logic.

(A) their intellectual advantage is greater in skills underlying reading ability and nonverbal logic
(B) their intellectual advantage is the greater in skills underlaying reading ability and nonverbal logic
(C) the greater their intellectual advantage in skills underlying reading ability and nonverbal logic
(D) in skills that underlay reading ability and nonverbal logic, their intellectual advantage is the greater
(E) in skills underlying reading ability and nonverbal logic, the greater intellectual advantage is theirs


OA is C

Do you not need a verb in the dependent clause? If not why not?