Hello, I'm an expert in English grammar and I'd be happy to help you understand when to use "do" and "does".

In English, "do" and "does" are auxiliary verbs used to form questions and negative statements in the simple present tense. Here's when to use each one:

1. **Use "do" with plural subjects and with the pronouns "I," "you," "we," and "they."**
- For example: "We do our homework every day."

2. **Use "does" with singular third-person subjects, which are he, she, it, or singular nouns.**
- For example: "She does her homework every day."

It's important to note that "do" and "does" change form to "did" for questions and negatives in the simple past tense.

Now, let's translate that into Chinese:

大家好，我是英语语法方面的专家，很高兴能帮助您理解何时使用 "do" 和 "does"。

在英语中，“do” 和 “does” 是助动词，用于构成一般现在时的疑问句和否定句。以下是使用它们的时机：

1. **当主语是复数，或者是代词 "I"、"you"、"we" 和 "they" 时，使用 "do"。**
- 例如："We do our homework every day."

2. **当主语是第三人称单数，即他、她、它或单数名词时，使用 "does"。**
- 例如："She does her homework every day."

需要注意的是，在一般过去时的疑问句和否定句中，"do" 和 "does" 会变化成 "did"。

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Yes, I do.Do. We use do when the subject is I, you, we or they.Does. We use does with third person singular pronouns i.e when the subject is he, she or it.Past Tense. Did is the past form of both do and does.Negatives. The negative form of do is do not.read more >>