16．－Governments at all levels have to take measures to improve the quality of basic education.

－Exactly. _________, students' homework must be greatly reduced.

A．That's to say

B．What's more

C．Believe it or not

D．In a word

小麦高秆（D）对矮秆（d）为显性，抗锈病（R）对感锈病（r）为显性，现以高秆抗锈×矮秆感锈，杂交子代分离出15株高秆抗锈，17株高秆感锈，14株矮秆抗锈，16株矮秆感锈，可知其亲本基因型为（）。

A.Ddrr×ddRr

B.DdRR×ddrr

C.DdRr×ddrr

D.DDRr×ddrr