疑问词 + to 不定式

疑问词 + to + 动词原形 就像句子里的一个小问句：what to do = what I should do，where to go = where I should go。它常放在 know、decide、learn、remember、ask、explain、tell、show… 后面。

💡中文说“不知道说什么”，疑问词后面直接跟动词，所以学习者常常漏掉 to（不说：I don't know what say）。记住：疑问词 + to + 动词。

1. 说自己不知道或不确定该做什么

• We're lost. We don't know which way to go.

  我们迷路了。我们不知道该往哪边走。

• I'm not sure what to wear to the interview.

  我不确定面试该穿什么。

2. 礼貌地问路或询问做法

• Excuse me, can you tell me how to get to the bus station?

  打扰一下，能告诉我怎么去汽车站吗？

• Do you know where to park around here?

  你知道这附近哪里可以停车吗？

3. 学习、教或演示怎样做某事——learn / teach / show + how to

• I learned how to swim when I was six.

  我六岁的时候学会了游泳。

• Can you show me how to use this machine?

  你能教我怎么用这台机器吗？

4. 决定、记得、忘记——decide / remember / forget + 疑问词 + to

• Have you decided where to go for your holiday?

  你决定好假期去哪儿了吗？

• I always forget how to spell “necessary”.

  我总是忘记 “necessary” 怎么拼。

和 tell、show、teach、ask 连用时，人紧跟在动词后面，放在疑问词之前。Explain 不一样：要说 explain to me how to…，或者不提人：explain how to…

• She showed me how to fold a paper crane.

  她教我怎么折纸鹤。

• Could you explain to me what to do next?

  你能给我解释一下接下来该做什么吗？（不说：explain me）

• Nobody told us when to start.

  没人告诉我们什么时候开始。

疑问词 + to 不定式表示某人应该 / 可以做什么，做这件事的人就是主语（或句中提到的那个人）。要谈论别人或一个事实，就用陈述语序的完整从句。

• why 一般不这样用：I don't know why I should go（不说：why to go）。
• to 不定式前面用 whether，不用 if：I'm not sure whether to call him.
• 在 learn 后面，how 可有可无：learn to swim = learn how to swim。
• 这个句型也可以放在形容词和名词后面：I'm not sure what to do. · I have no idea where to start.

• ✗I don't know what should I say.

  ✓I don't know what to say.

  用 what to + 动词（或者用陈述语序 what I should say）。

• ✗Can you tell me how to getting to the station?

  ✓Can you tell me how to get to the station?

  to 后面用动词原形。

• ✗We didn't know where go next.

  ✓We didn't know where to go next.

  不要漏掉 to。

• ✗I'm not sure if to call him.

  ✓I'm not sure whether to call him.

  to 不定式前面用 whether，不用 if。

• ✗Please tell me where should I wait.

  ✓Please tell me where to wait.

  句子里面的问句不用疑问语序。

• ✗Can you explain me how to use it?

  ✓Can you explain to me how to use it?

  explain to + 人。