It was not until early this morning my father came back from work, which surprised us.
A. when
B. where
C. that
D. who
网友回答
A. when
B. where
(答案→)C. that
D. who
解析：考查强调句型。本题强调的是时间状语not until early this morning；句意：直到今天早晨早些时候，我的父亲才下班回来，这让我很惊讶。It is/was…that/who…是强调句型的基本结构，故C正确。