B . Đồng bằng sông Cửu Long 

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We often play basketball ____ the weekends.

1. You should take the train instead of the bus.

-> If....................................................................................................................

2. I'm sure that someone forgot to lock the door.

--> Someone must.............................................. 

3. They bought this house ten years ago.

--> They have.............................................. ..................................................

4. The course finished with a big party.

--> At the end............................................... ................................................

5. We invited a pop star onto the chat show, but he didn't turn up.

--> The pop star................................................................................................