The doctor insisted that I give up smoking.

I suggest that we go tomorrow.

I suggest we go the next day. I suggest that we leave the next day.

We learned from his letter that he was in Spain. From his letter, we know that he is in Spain.

I don't know where he will arrive in time. I don't know whether he can arrive in time.

I don't know what they like about this place. I don't know if they like this place.

I'll see if I can persuade him to accept it. I'll see if I can persuade him to accept it.

I asked her when she agreed. I asked her if she agreed.

10, I don't know if it is big enough. I don't know if it is big enough.