Could / should / have to / must
A: Hi, Robert. How’s it going?
R: Very good. And you?
A: Terrible. I got low score in speech communication of the mid-term.
R: Are you kidding? Howard gave us information of the test 2 weeks ago. You didn’t prepare it, did you?
A: It’s not like that. I spent a lot of time on it. I could have done better on the test, but I ran out of time.
R: Forget it, face the fact. He always gives students low score. You shouldn’t put everything in it. You should shorten the content of your speech.
A: I got it. Could I borrow your cell phone for a minute? My cell phone battery is dead.
R: You could, but I’m expecting a call, so don’t take long. See. This is my new cell phone. I bought it last week. Here you are.
A: Wow! I phone 7. It’s brand new and hit. But a lot people said it’s not really good. You shouldn’t have bought this cell phone.
R: It’s none of your business. Hurry up! I need my phone.
A: Take it easy. You have to sell you phone while it’s hit. If I were you, I wouldn’t buy it.
R: That’s enough! I must be losing it to buy the phone. Or sell you in the cheapest price.
A: Come on, I’m not an idiot.