Goodness/God/Heaven/Christ knows

used to mean "I don't know" or to emphasize a statement. Some people may find this use offensive.

(表示不知道或加强语气)天知道(有些人认为此种表达具冒犯意)

God only knows what'll happen next!

只有老天爷知道接下来会发生什么!

Take your shirt off - Heaven knows it's hot enough today!

把衬衫脱了——今天可够热的!