1. It was essential___________________(在截止日期前寄回申请表)。
　　2.I went to see William,__________________(结果发现他前两天已经走了)。
　　3.He flatly contradicted the audience was instantaneous; no sooner ____________________(讲演刚结束，听众就爆发了热烈的掌声)。
　　4.Should it rains,____________________(农作物就得救了)。