Many workers were organized to clear away ________ remained of the           World Trade Center.

I can still remember that it is since the 1990’s, _____ we began to use cell phones,_______ the number of mobile users has greatly increased．

Neighbors said they heard the man tell the woman that she couldn’t leave______ she gave back the money borrowed from him.

Choosing the right dictionary depends on ________ you want to use it for.

I meant to help him . ______， he didn’t accept my offer.