There is a _____ of understanding between them.Otherwise,they will be good friends.
问题描述：
There is a _____ of understanding between them.Otherwise,they will be good friends.
A.sufficiency B.abundance C.adequacy D.lack
答
A(足够)B(过量)C(充足)从意思上并且BC从语法上（应该用an）都不正确.
后面说：否则,他们将是很好的朋友.所以前面应该是彼此之间缺乏了解.
选择D