常考的強調句結構是it 引導的句子。
it is (was) 被強調部分+ that (who) + 句子其他部分。
此結構強調的成分僅限於主語，賓語和狀語。
it is from the sun that we get light and heat.
it was not until i had read your letter that i understood the true state of affairs.
典型例題
1） it was last night ___ i see the comet.
a. the time b. when c. thatd. which
答案c. 強調句的結構是： it +be +強調部分 + that (who) + 主謂句。 強調句的連詞只有兩個，that和who。當強調的部分是人，且為句子的主語時，才用 "who"，其餘用that。
原句： my father did the experiment in the lab yesterday evening.
強調主語： it was my father who did the experiment in the lab yesterday evening.
強調賓語： it was the experiment that my father did in the lab yesterday evening.
強調時間： it was yesterday evening that my father did the experiment in the lab. (注意不用when)
強調地點： it was in the lab that my father did the experiment yesterday evening.
2）it is ten years ___ miss green returned to canada.
a. that b. when c. since d. as
答案c. 考點是連詞用法。 本題易誤選為a. that. 其實本句不是強調句。若是，去掉it be… that還應是一個完整的句子。而本句去掉 'it is…that'，只剩下ten years miss green returned to canada. 不成句。因此本句不是強調句。
it is /was +時間+ since… 其中is<---> has been was <---> had been.