Lucy does her homework very ________. She is ________ than Lily.

A．carefully, much more careful

B．carefully, much carefuller

C．careful, many more careful

D．careful, a little carefuler

水泥混凝土面层混凝土配合比应保证混凝土的（）等要求。

A.设计强度

B.耐久性

C.耐磨性

D.抗冻性和混凝土拌合物的和易性