It was ten years _______ he returned to his hometown and set out to revenge his dead father.

Exactly______ the potato was introduced into Europe is uncertain, but it was probably around 1565.

________ I meet him, I always think of the things which happened between us.

You often say that everyone should be equal, and this is ____Ｉdisagree.

____ you know your potential（潜力）, you have to rely on many other people to get to where you are.