Can you please check these sentences, too? Thank you. I just wonder if you could use these expressions in a common conversation.

1) I sent John three letters but he hasn't replied (not didn't reply)to any of them.
2) When did you get that jacket? I haven't noticed (not didn't notice) it before.
3) Would you mind if I opened the window? I'd rather leave it closed (but you left it closed)/Yes, I wouldn't./No, I wouldn't/No, not at all.
4) Is it all right if I leave it closed? No, it isn't./Yes, I don't mind. (?)
5)Do you mind if I open the window? Yes, I do/No, I don't./No, I don't mind/ I don't
6)Can I open the window? Yes, you can.No, you can't. No , not at all. (??)

1) I sent John three letters, but he hasn't replied to any of them.

2) When did you get that jacket? I haven't noticed it before.

3) Would you mind if I opened the window? I'd rather leave it closed. /Yes, I wouldn't. /No, I wouldn't./ No, not at all.

4) Is it all right if I leave it closed? No, it isn't./ Yes, I don't mind.

5)Do you mind if I open the window? Yes, I do./ No, I don't./ No, I don't mind.

6)Can I open the window? Yes, you can. No, you can't.

1) The sentence "I sent John three letters but he hasn't replied to any of them" is grammatically correct and can be used in common conversation. The use of "hasn't replied" implies that John has not responded to any of the three letters sent.

2) The sentence "When did you get that jacket? I haven't noticed it before" is also grammatically correct and can be used in common conversation. The use of "haven't noticed" indicates that the speaker did not observe or recognize the jacket until now.

3) The sentence "Would you mind if I opened the window? I'd rather leave it closed" is grammatically correct and appropriate for a conversation. The speaker is requesting permission to open the window, but then expresses a preference to keep it closed after all. The response options "Yes, I wouldn't," "No, I wouldn't," and "No, not at all" are all appropriate depending on the speaker's preference.

4) The sentence "Is it all right if I leave it closed? No, it isn't. Yes, I don't mind." is a bit confusing and unclear. It would be better to rephrase it. For example, you could say, "Is it okay if I keep it closed?" and the response options "Yes, I don't mind" or "No, it isn't" would work in that scenario.

5) The sentence "Do you mind if I open the window? Yes, I do/No, I don't./No, I don't mind/ I don't" is grammatically correct and can be used in common conversation. The speaker is asking for permission to open the window, and the response options provide different answers indicating whether the person minds or not.

6) The sentence "Can I open the window? Yes, you can. No, you can't. No, not at all." is grammatically correct and suitable for common conversation. The speaker is seeking permission to open the window, and the response options provide different answers indicating whether the person is allowed to open the window or not.