下列句子中每句都有一处错误，请在错误处画线，并将正确的答案添在句后的横线上。
If you have questions to ask, please rise your hand.________
When you take a taxi, please make sure you ask a receipt.________
During the holidays, places of interest in Beijing often get very crowd.________
The building on construction is a post office.________
Alleys of old Beijing are very narrow. Tricycles are very worth using.________
Buses numbering 200 to 210 are still on duty at night.________