【正确答案】 C

【答案解析】[理由] 空格前有Whether引导的完整名词从句“Whether this book should be published in hardback or paperback”
(这本书是否以精装本或是平装本发行)，得知名词从句作主语时，等于单数名词，故知空格内应置入单数动词is，因此(C)应为正选。
名词从句共有3种：
1) 以that引导的名词从句
that he is nice(他人很好)
that he doesn't study(他不念书)
2) 以whether引导的名词从句whether he will come or not(他是否会来)
whether he will do it or not(他是否会做这件事)
3) 以疑问词(where、who、what、when...等)引导的名词从旬
where he came from(他来自何方)
how he will do it(他会如何做这件事)
when you will come(你何时会来)
以上名词从句作主语时均视为单数，故之后均使用单数动词。
[例] That he doesn't study makes his father angry.
(他不念书这件事使他爸爸很生气。)
Whether they will come or not is unknown.
(他们是否会来还不知道。)
When he will come remains to be seen.
(他何时会来有待观察。)
不过名词从句作主语时，均可用代名词it代替。故上列各例句也可改写如下：
It makes his father angry that he doesn't study.
It is unknown whether they will come or not.
It remains to be seen when he will come.