1）只能 This is the only choice.
I don't have enough money. I can only buy the cheapest ticket.
It's raining today. We have to stay in the hotel. We can't go out.
We don't have much time today. We can only go to on place.
2）尽量 as best we can, the best of our abilities, as much as possible
Tomorrow's meeting is really important. Everyone make sure that you can attend.
When we are traveling, we should take as little luggage as possible.
I'll come back as soon as I can.
3）把握 confidence ,sureness
I'm not sure that I would be able to climb to the top of the mountain.
We are not sure that we would be able to reserve the train tickets for tomorrow.
We are not sure that we can find the painting you are looking for.
4）就 sth. will happen soon
The student who are going south are leaving tomorrow.
I'm going to Shanghai, but I'll come back in 3 days.
As soon as we have some news, we'll let you know.
Substitution and Extension
1）V+回来 the result of action are returned to the original spot.
Yesterday she brought a lot of tasty things back.
（knocking on room door）
Xuemei：Just a minute.
staff：I’m from housekeeping, I’ve come to collect the laundry.
Xuemei：Please come in. The clothes are here.
staff：Let me see. Madam, this shirt is missing a button.
staff：Do you have any requirements for laundering these garments？
Xuemei：These garments need to be drycleaned. This one is easy to shrink, please don’t wash it in water.
Xuemei：This shirt has a stain on the sleeve, can it be washed off？
staff：Let’s see, what is this? It looks like soy sauce.
Xuemei：It may be soy sauce.
staff：We can try our best.
Xuemei：You can’t get it off？
staff：We’re not sure whether it can be washed off.
staff：I take it these garments all need to be pressed!
Xuemei：Of course, they need to be pressed after they’re cleaned.
staff：Sure, I’ve taken that down.
Xuemei：How long does it take？
staff：We can bring it back tomorrow afternoon.
Xuemei：How do I pay？
staff：You can pay when you check out as part of your room bill.
staff：Please confirm the number of garments and your laundry requirements.
staff：If it’s all OK, please sign here.
Xuemei：Sorry, just let me see if there’s anything in my daughter ’s clothes？
staff：This must be the one you’re talking about？
Xuemei：Yes, let me check the pockets. There really is something. （Takes out many items）