短文改错

It is interesting to visit foreign country,but there

1.________

are some problems if we know the language very well.

2.________

It may be difficulty to talk with the people there.

3.________

We may don't know how to use the telephone there.

4.________

We may not know how to buy things we needs.

5.________

In a strange country,we may not know where to be eat or what to order in a restaurant.

6.________

When we need help,we may not know how to ask help.

7.________

It was not a happy thing to have an experience like that.

8.________

在一定条件下，当高速的（）打击在金属表面上时，就在金属表面上产生了X射线。

A.正离子

B.自由电子

C.分子

D.原子