Whether he will come or not is still a question.

　　他是否会来仍然是个问题。

　　Whoever breaks this law deserves a fine.

　　违反该法者应予以罚款。

　　When the plane is to take off has not been announced.飞机何时起飞还没有宣布。

　　It is known to all that light travels in straight lines.

　　众所周知，光沿直线传播。

　　[即时演练1]　单句改错

　　①Bob failed in the exam disappointed his parents.

　　Bob前加That

　　②If Peter will attend the ceremony remains unknown.If→Whether

　　③That Alice said at the meeting was of great value.

　　That→What

　　三、表语从句

　　1．表语从句是在复合句中作表语的名词性从句，放在系动词之后，一般结构是"主语＋系动词＋表语从句"。可以接表语从句的系动词有be，look，seem等。表语从句通常由连词that，whether，连接代词和连接副词，以及as if，as though，because等连词引导。

　　The girl is not what she was ten years ago.

　　这个女孩已经不是10年前的她了。

　　It looks as if it is going to rain.

　　看起来像是要下雨了。

　　The question is whether we should accept their invitation.问题是我们是否应该接受他们的邀请。

　　This is why we put off the meeting.

　　这就是我们推迟会议的原因。

　　2．当主语是reason时，表语从句一般要用that引导而不用because。

　　The reason why Peter hasn't come is that he did not catch the train.

　　彼得还没有来的原因是他没赶上火车。

3．如果主句的主语是advice，suggestion，order，request，requirement等表示"建议、命令、请求"的名词时，其后的表语从句要用虚拟语气，谓语形式是should