It was because of his illness the meeting had to be put off.
A. which
B. what
C. that
D. so that
网友回答
A. which
B. what
(答案→)C. that
D. so that
解析：考察强调句型。本句是一个强调句型，强调句型的基本结构为It is/was被强调成分that/who其它成分；其最大的特点就是去掉it is/was…that/who…句子仍然成立。要注意强调句型能强调除谓语动词以为的所有的句子成分。在考查的时候，经常会把强调句型和定语从句结合在一起考查，要注意分析句子的成分。本句强调的原因状语。故C正确。