银汞合金的最佳塑形时间为()
A.1~15分钟
B.5~15分钟
C.15~20分钟
D.20~25分钟
E.20分钟以后
参考答案:C
Mary is ill today. If she ______ ill, she _______ absent from school.
A.weren’t; couldn’t be
B.wasn’t; wouldn’t have been
C.wasn’t; wouldn’t be
D. weren’t; won’t be
温室花卉出棚前,必须对其进行锻炼,在进棚前,要对温室进行消毒和维修。