I need hardly tell you that the work is dangerous.

　　這工作很危險，這就不用我說了。

　　It would be dangerous for you to stay here.

　　你待在這兒不安全。

　　Seriously though, it could be really dangerous.

　　不過說實在的，這事說不好真的很危險。

　　The traffic here is very dangerous for children.

　　這里的交通對孩子很危險。

　　You're on dangerous ground if you criticize his family.

　　你要是批評他的家人可就惹麻煩了。