Besides the content of a book, the editor also cares about is the number of readers.
A. who
B. why
C. how
D. what
网友回答
A. who
B. why
C. how
(答案→)D. what
解析：D 考察名词性从句。句意：除来了书的内容，编辑还关心读者的数量。在句中 the editor also cares about是主语从句，空格在从句中做care about的宾语，应该使用what作为引导词。故D正确。