“Underground” is the only word in the English language _____ begins and ends with the letters “und”.

My father is teacher. He loves________ students very much.

Gary: I can’t find my pen.   Nina: Is the one on Jack’s desk 　　　? Gary: Yes, Thank you. 

---When shall we meet again next week?--- ____ day is possible. It’s no problem with me.

She looks very sad. I want to help her, but I just don’t know ____ to do it.