根据下列句子，适当的单词，补全句子。

l You are not allowed                            in the museum.

2. No        is allowed in a doctor's waiting-room.

3. Do you allow me                here?    -No, I’m afraid you can't

park your car here.

4.   KEEP  QUIET  You are not allowed _                          in a reading-room

or a library.

5. Don't you see the sign at the beach? _       is not

permitted. It's dangerous.

6.   The sign means "                     "

管道运输的一次性固定投资大，但是运作成本低。