(2013·新课标Ⅱ，10)It was only after he had read the papers________Mr.Gross realized the task before him was extremely difficult to complete.

A．when

B．that

C．which

D．what

耳廓多毛症总是由父亲传给儿子，又由儿子传给孙子，决定这个性状的基因最可能在（）

A.常染色体上

B.Y染色体上

C.X染色体上

D.X、Y染色体上