【单选题】下面哪种不是古罗马时期出现的建筑类型 ?
【单选题】The separation of impurities and water from ______is essential for good combustion of diesel engines.
【简答题】通常,root的主目录为_______________。
【单选题】发送电子邮件时,如果接收方没有开机,那么邮件将( )。
【单选题】_______he retires, Prof. Baker will have taught in the university for almost forty years.