Okay, let's fill in the blanks with the correct forms of 'do' and 'does'. Remember, 'does' is used for third-person singular (he, she, it), and 'do' is used for everything else (I, you, we, they).
A: Does Helen take the bus?
B: Yes, she does.
Explanation: 'Helen' is a third-person singular subject, so we use 'does'. The short answer also uses 'does' to agree with the question.
A: Do I need my book?
B: No, you don't.
Explanation: Even though the question is about 'I', we use 'do' because the person answering is saying what 'you' (the person who asked) needs. The negative short answer requires 'don't'.
A: Does a lion eat leaves?
B: No, it doesn't.
Explanation: 'A lion' is singular and can be replaced with 'it', so we use 'does'. The negative short answer is 'doesn't'.
A: Do you want milk?
B: No, I don't.
Explanation: With 'you', we use 'do'. The negative short answer requires 'don't'.
A: Do you live in a big house?
B: Yes, we do.
Explanation: With 'you', we use 'do'. The positive short answer uses 'do' to agree with the question.