A new study finds that the more hostility people show in their behavior and attitudes, then calcium deposits are more likely to be in the arteries of their hearts.
A. then calcium deposits are more likely to be
B. then the more likely calcium deposits are
C. the more there are likely to be calcium deposits
D. the more likely they are to have calcium deposits
E. the more likely there are to be calcium deposits

This is a GMAT Prep question

This is a simple question I know D is correct . still I want to clarify one thing

When we say "The more X, the more Y " do we need connector in between or it is idiom and the two parts {"The more X, <no connector> the more Y "} are connected with out connector