问题补充：
They have producedthey did last year.
A. twice more grain as
B. twice as much grain as
C. twice as many grain as
D. as twice many grain as
答案：
A. twice more grain as
(答案→)B. twice as much grain as
C. twice as many grain as
D. as twice many grain as
解析：grain是不可数名词。倍数放在最前面。不论哪种表示法，主语、谓语之后都应先加上倍数，所以首先排除D。若选A，more应与than搭配，所以此选项也可排除。grain是不可数名词，应用much修饰，所以排除C。
