名詞・副詞を “It is ~ that” の ~ 部分に入れて強調する.
基本パターン
元の文 Tom played tennis with Mary yesterday.
S(名詞)を強調 It was Tom that played tennis with Mary yesterday.
O(名詞)を強調 It was tennis that Tom played with Mary yesterday.
adverb(副詞)を強調 It was with Mary that Tom played tennis yesterday. It was yesterday that Tom played tennis with Mary.
過去形だが was → isとなるパターン
It is tennis that Tom played with Mary yesterday.
原則は 過去形 → was
Who, Which, When となるパターン
It was Tom who played with Mary yesterday.
基本的にはWho以外は使われない
That の省略
It was tennis (that) Tom played with Mary yesterday.
疑問文
Tom played tennis with Mary yesterday.
What was it that Tom played with Mary yesterday?
Who was it that played tennis with Mary yesterday?
How was it that Tom finished his work?
形式主語(仮主語)との違い
仮主語 → 主語を短くするための用法
Continuing studying English is difficult. → It is difficult to continue studying English.