“It + be + 时间名词+before / since”从句句型中用before引导时，句意是 “过了多久才……”，主句中的be动词为过去时或将来时态；用since引导时，其句间是“自从……以来已经多久了”，主句中的be动词多为现在时(或现在完成时)或一般过去时。

根据下列句意及汉语注释提示，在句子右边横线上写出空缺处各单词的正确形式。

1．Examine the results carefully,and you will make a ________（结论）．    1．________

2．His first speech as president made a strong i______on his audience．         2．________

3．I keep my reference books near my desk for________ （方便）．          3．________

4．The restaurant has just e________five new waiters．                               4．________

5．We should___（防卫）our country from the attack of other countries．   5．________