主语从句在复合句中充当主语成分，通常放在句首，引导主语从句的词有连词that、whether，连接代词what、who、whose以及连接副词how、wh...

主语从句在复合句中充当主语成分，通常放在句首，引导主语从句的词有连词that、whether，连接代词what、who、whose以及连接副词how、when、where等。引导主语从句的词连词that和whether连词that在主语从句中不充当任何成分，只起连接作用，没有任何实际意义，通常可以省略；而连词whether在主语从句中不充当任何成分，表示“是否”之意，不能省略。例如：That the planet is warming is now undeniable（地球正在变暖这一点已经无可否认）Whether the strike will be called off remains to be seen（罢工是否会被取消还有待观察）连接代词what、who、whose连接代词在主语从句中充当名词性成分，不可省略。例如：What the government should do is to provide more job opportunities（政府应该做的是提供更多的就业机会）Who will be sent to represent the country is still unknown（谁会被派去代表这个国家仍然未知）Whose victory in the election was unexpected（选举中的胜利出乎意料）连接副词how、when、where连接副词在主语从句中充当状语成分，不可省略。例如：How the missing plane could have disappeared without a trace remains a mystery（这架失踪的飞机是如何无影无踪地消失的仍然是个谜）When the new president is elected will have a significant impact on the future of the country（新总统何时当选将对国家的未来产生重大影响）Where the emergency meeting will be held has not yet been announced（紧急会议在哪里召开尚未宣布）主语从句的类型陈述句型主语从句陈述句型主语从句由连词that引导，例如：That the new bridge will be completed next year is certain（新桥明年将建成是确定无疑的）That most of the earth's surface is covered by water is true（地球表面的大部分被水覆盖是事实）疑问句型主语从句疑问句型主语从句由连接代词或连接副词引导，例如：How the missing plane could have disappeared without a trace remains a mystery（这架失踪的飞机是如何无影无踪地消失的仍然是个谜）When the new president is elected will have a significant impact on the future of the country（新总统何时当选将对国家的未来产生重大影响）祈使句型主语从句祈使句型主语从句由连词that或省略连词引导，例如：Let's see if there is any improvement（让我们看看是否有任何改进）（省略连词）It's important that we should not panic（重要的是我们不应该惊慌）（连词that）三、主语从句的时态和语态主语从句的时态主语从句的时态通常与主句保持一致，根据语境选择合适的时态。例如：When the project is completed will depend on the weather（工程何时完成将取决于天气）（一般将来时）That the spacecraft was launched on time was a relief（宇宙飞船按时发射令人松了一口气）（一般过去时）Whether the company will go bankrupt remains to be seen（这家公司是否会破产还有待观察）（一般现在时）主语从句的语态主语从句的语态根据从句中的主语和谓语的关系而定。如果从句中的主语是动作的执行者，则使用主动语态；如果从句中的主语是动作的承受者，则使用被动语态。例如：That the bank was robbed last night is shocking（这家银行昨晚被抢劫了令人震惊）（被动语态）Who will win the election remains to be seen（谁将赢得选举还有待观察）（被动语态）What they are working on is a secret（他们正在研究什么是个秘密）（主动语态）主语从句的强调为了强调主语从句，可以使用强调句型“It is/was+被强调部分+that/who+其他部分”。例如：It is not who rules us that is importantbut how he rules us（重要的不是谁统治我们，而是他如何统治我们）It was the book that he read yesterday that made him late（他昨天读的那本书让他迟到了）主语从句中的虚拟语气在某些情况下，主语从句中需要使用虚拟语气。虚拟语气通常用于表示与实际情况相反的情况，或者表示主观愿望和假设。例如：If only I had known the answer（要是早知道答案就好了）（虚拟语气）It would be wonderful if we could travel to the moon（如果我们能去月球旅行就好了）（虚拟语气）主语从句的位置变化主语从句通常放在句首，但有时为了平衡句子结构或强调某个信息，也可以将主语从句放在句中或句末。例如：That the project was cancelled came as a surprise to everyone（项目被取消了这让每个人都感到意外）（主语从句放在句首）The news that we won the game was encouraging（我们赢了比赛的消息令人鼓舞）（主语从句放在句中）The company has yet to determine who will be assigned the task（公司尚未决定谁将负责这项任务）（主语从句放在句末）