1.We usually find this signin a museum.（对划线部分提问）

  you usually find this sign?

2.This sign tells us not to jump into the water.（对划线部分提问）

  this sign tell us?

3.We can't fish here.（保持原句意思）

is nothere.

4.This sign means: People mustn't swim.（对划线部分提问）

; this sign

5.steam, down, when,cools, happens, what（连词成句）