這是一個主語從句.而It"s .that是強調句
（1）主語從句.
It is important that students today master English.
It is reported that China will send up a series of spaceships in the 21st century.
It is a rule that everyone should obey the State’s laws.
It happened that they were out visiting their friends.
可以看出,此類主語從句的句子成分無論是主語、謂語、賓語,還是各種狀語都是完整的,並且不能稱到“It is…”結構中去.這就是判別主語從句的基本點.
（2）強調句.
先舉一個重點成分句：昨天我在書店看見了他.I saw him at the bookstore yesterday.
現將此句變成分別突出主語、賓語、地點及時間狀語的強調句：
A、It was I that/who saw him at the bookstore yesterday.
B、It was him that I saw at the bookstore yesterday.
C、It was at bookstore that I saw him yesterday.
D、It was yesterday that I saw him at the bookstore.
這是一個主語從句.而It"s .that是強調句
（1）主語從句.
It is important that students today master English.
It is reported that China will send up a series of spaceships in the 21st century.
It is a rule that everyone should obey the State’s laws.
It happened that they were out visiting their friends.
可以看出,此類主語從句的句子成分無論是主語、謂語、賓語,還是各種狀語都是完整的,並且不能稱到“It is…”結構中去.這就是判別主語從句的基本點.
（2）強調句.
先舉一個重點成分句：昨天我在書店看見了他.I saw him at the bookstore yesterday.
現將此句變成分別突出主語、賓語、地點及時間狀語的強調句：
A、It was I that/who saw him at the bookstore yesterday.
B、It was him that I saw at the bookstore yesterday.
C、It was at bookstore that I saw him yesterday.
D、It was yesterday that I saw him at the bookstore.