1.
If occurs the accident, stir 999.
如果发生事故，拨999。
2.
Supposing（ that） there was an earthquake, what would be the right way to escape?
如果发生地震，正确的逃生方法是什么？
3.
Discontinue use if irritation or rash appear.
如果发生刺激或丘疹请停止使用。
4.
If an erroneous display or operation occurs
如果发生错误的显示或操作时
5.
If lightning strikes, the haystack will be burned up in no time
如果发生雷击，这干草堆会很快烧毁。
6.
In case of fire, ring (up) the police.
如果发生火灾，打电话报警。
7.
A loss in volume will occur if infiltration takes place.
如果发生了渗润作用，水量就会减少。
8.
If there are disturbances in Hong Kong, the Central Government will intervene.
如果发生动乱，中央政府就要加以干预。
9.
Bob's your uncle when ..
如果发生…的情况，请不必着急。
10.
Ring the police if there is a burglary.
如果发生入户盗窃就给警方打电话。
11.
If she is feverish,telephone the doctor.
如果他发烧给医生打电话。
12.
Otherwise, decay process is forbidden.
如果不是这样，就不会发生这样的衰变。
13.
Supposing it were true, what would happen?
如果那是真的，将会发生什麽事？
14.
If she catches you reading a novel in class, she will be angry.
如果她发现你上课读小说,她会生气的.
15.
When this happens, they will tear up the contract.
如果这事发生, 他们将会违约。
16.
If this thread already has the lock, a deadlock ensues.
如果线程已经得到锁，会发生死锁。
17.
They will be in danger if they are rebellious.
如果他们造反，他们就要发生危险。
18.
If the aims of two countries colide,there may be a war.
如果两国的目标冲突，就可能发生战争。