If _______ unsolved, this may lead to more serious problems.
187. Yesterday we had a long meeting whichfour hours.
186. I only _______ him from my wife, but I have never met him.
185. Hello! I_______ you _______ in London. How long have you been here?
184. There's no wind now. We can't _______ kites on the playground.
183. This plan will help to _______ two birds with one stone.