Thank you, Writeacher. I left out the following sentences. Thank you very much.
1) Who has called the wrong number?
His team has always been (or have always been?) worse than the others.
2) Have you read that book yet? No, I haven't finished it yet.
3) I've never flown in a helicopter before. My mum is cross with me. I must do my homework this afternoon.
4) John doesn't have to take the car, we can walk to school.
You don't have to buy any drinks. There are plenty in the fridge.
5) Stop that, Mary! You mustn't chew when you're speaking.
You mustn't throw the class register at your teacher.
6) If you keep misbehaving I'll reprimand you (I'll write a reprimand).
I've known Mary since I started university.
1. ... team has ...
4. This is a run-on. How will you fix it?
http://grammar.ccc.commnet.edu/grammar/runons.htm
6. comma needed
Everything else is fine.
1) To determine who has called the wrong number, you would need more information. In this sentence, the subject is "His team." Since "team" is a collective noun, it can be treated as singular or plural. In this case, you can use either "has always been" or "have always been" depending on whether you view the team as a single unit or as individual members.
2) To answer the question if someone has read a book, you can use the simple present perfect tense. In the negative form, you would say, "No, I haven't finished it yet," indicating that the book hasn't been fully read.
3) In this sentence, the speaker is mentioning two separate things. The first part, "I've never flown in a helicopter before," is a statement about the speaker's past experience. The second part, "My mum is cross with me. I must do my homework this afternoon," is a consequence or an intention of the speaker. It does not directly relate to the first statement about flying in a helicopter.
4) The first sentence is suggesting that John does not need to take the car because the option of walking to school is available. The phrase "have to" implies necessity, and "doesn't have to" means the absence of necessity. In the second sentence, "You don't have to buy any drinks," indicates that it is not necessary to buy drinks as there are already enough in the fridge.
5) "Mustn't" is used to express prohibition or something that is not allowed. In the first sentence, "You mustn't chew when you're speaking," it is indicating that chewing while speaking is not allowed. In the second sentence, "You mustn't throw the class register at your teacher," it is emphasizing the prohibition of throwing the register at the teacher.
6) The first sentence, "If you keep misbehaving, I'll reprimand you (I'll write a reprimand)," is stating a consequence or action that will occur if someone continues to misbehave. In the second sentence, "I've known Mary since I started university," it indicates that the speaker has known Mary from the time they began studying at university.