1.My hotel room overlooked a courtyard,in which there was a fountain and several trees.（定語從句）
2.Uncle Charles looked everywhere for his glasses, he could not find them though.(放在此處比較口語化,置于句首也可以)
3.During Christmas,there was so much extra work at the post office that a great number of students were employed to help.(so...that...意為：如此...以至于）which 的后面為什么要加there??？然后那個第一句能不能這樣改：My hotel room in which overlooked a courtyard as a fountain and has several trees.非常感謝！in which引導了后面的定語從句。there be 表示存在的“有”啊，總不能用have 吧。不能那樣改，語法上不通。這句話的意思是：我住的旅店房間能看到一個院子，那里有一座噴泉和幾株樹。