The signs_____the lake say"No fishing".

in the library we can see the sign which says NO TALKING .
In the hospital, we can also see a lot of signs ,some of which say no smoking and others of which say no making noise

选a,round 和around的意思相近,但用法不完全相同.
异同如下:
around round 
作介词用的around与round通常可以互换,只不过美语常用around,而英语常用round,例如：You can see the post office round/around that corner.(绕过那个弯你就可以看到邮局.但是一定要区别它们的不同之处：round可以用作形容词、副词、介词、动词、名词；而around只能用作副词或介词.例如：The post office is just round (around) the house (用作介词).He has round face (用作形容词).The river rounded the stones.(用作动词)
1.在表示"圆形运转,回到原处","环绕","周围"时,英语用round,但美国人用around,例如:
The earth revolves round(around)the sun(地球绕太阳运行).
They sat round(around)the table.(他们围着桌子而坐)
New things are happening all round(around) us(新事物在我们周围不断发生)
There is a small restaurant round(around)the corner(绕过街角有一家小餐馆).
2.美国人以及部分英国人也常用around表示"到处","无目的地","附近","左右"等较为模糊的概念,例如
The news that President Clinton was coming spread rapidly around the campus(Clinton 总统就要到来的消息很快地就在校园里传开啦)
3.around 还可以表示"不止一处","在许多地方","在不同地方".但在美国英语里,一般只用around,例如:
The students are standing around(学生们在到处站着)
They are rushing around in New York.(他们在New York到处奔波).