补全对话.

A: Where did you go on vacation?

B: I __1__ to Xi'an.

A: Xi'an?What did you do there?

B: I __2__ the Terra-Cotta Warriors.

A: Great! Did you __3__ yourself?

B: Yes,very much. How __4__ your vacation? Where did you go?

A: I visited Xinjiang. There were lots of grapes there and I like their music and dance

B: __5__ did you go there? Did you go there by plane?

A: No, I went there by train

每个工程项目都有其确定的终点，所有工程项目的实施都将达到其终点，这是工程项目的( )特征。

A．唯一性

B．一次性

C．整体性

D．不可逆转性