根据对话情景，在空白处填入恰当的句子，使对话完整通顺。

A: You look unhappy, Gina._______1_________ ?

B: My uncle is ill in Green Hospital. I need to see him, but I don't know where the hospital is.

A:  _______2_________ . Let's ask the policeman over there. 

    Excuse me, sir. ________3________Green Hospital?

C: Go down this street, and then turn right. At the end of the street you'll see it.

A: Can we take a bus there?

C: Yes, the No. 2 bus will take you there. Look! The bus stop is over there.

A: _______4_________ ?

C: About half an hour.

A: OK, thank you so much.

C:  ________5________ .    

一般情况下，只要严格遵守测量规范，仔细谨慎，认真检核观测结果，（）是可以避免和发现的。

A.误差

B.偶然误差

C.系统误差

D.粗差