单选题 20.  It was not until he arrived in class ______ realized he bad forgotten his book.
【正确答案】 B
【答案解析】 本题考查强调句型。强调句的形式为it is not until...that...,因此空格处必须有that,故B为正确选项。本句意思为:他直到走进教室才意识到自己忘了带书。