I don't think____possible to learn English well without ____memory work.[ ]

A. it; many

B. that; a large number of

C. one; a great deal of

D. it; a good deal of

目前世界上年产量最高的金属是铁，它的两种主要合金是______和______；它们的主要区别是______不同，用它们做饮具是利用了其______．