is not yet decided.A. Whether he will write the book B. Whether will he write the bookC. I

问题补充：

is not yet decided.

A. Whether he will write the book

B. Whether will he write the book

C. If he will write the book

D. If will he write the book

答案：

(答案→)A. Whether he will write the book

B. Whether will he write the book

C. If he will write the book

D. If will he write the book

解析：考查主语从句。主语从句应该使用陈述语序。排除BD，if不能引导主语从句，排除C项。结合句意可知A正确。句意：他是否会写这本书还没有决定。