The fire lasted about four hours _the firefighters could con

The fire lasted about four hours _the firefighters could control it.A.until B.before选B为什么?
直到消防员来大火已经持续4小时了 这么翻译应选A啊

① 如果主句（或简单句）中的谓语动词为延续性动词的肯定式,用until或before均可,但在意义上有一定的差别.如：
She lived in the house until he came back. 她在那所房子里一直住到他回来.（强调“到此为止”）
She lived in the house before he came back. 在他回来之前,她一直住在那所房子里.（强调“在……之前”）
② 如果主句（或简单句）中的谓语动词为非延续性动词的否定式,用until或before均可,且意义上没有差别.如：
The moon will not come out until / before the clouds disappear. 云散了月亮才会出现.
不同方面：
① 如果主句（或简单句）中的谓语动词为非延续性动词的肯定式,只能用before,不可用until.如：
He can come here before sunset. 在日落之前他能来这.
② 如果主句（或简单句）中的谓语动词为延续性动词的否定式,多用before,一般不用until.如：
He has not done anything before she comes. 在她来之前,他什么也没做.
③ 在It wasn't until ... that 强调结构中不用before.如：
It wasn't until this morning that I heard the news. 直到今天早上我才听到这个消息.
列情况下宜用before不用until.
1.主句为肯定式,谓语为终止性动词时只用before.
For example:
1). He fell asleep before I could take off his clothes.
2). We arrived there before it started to rain.
3). The holiday came to an end before I knew it.
4). He almost knocked me down before he saw me.
2.主句谓语动词强调动作的迟缓性,只用before,这时常伴有时间段状语或时间段暗示.
For example:
It was quite a long time before he found the elephant.过了很长时间,他才找到大象.
We had walked a long way before we found some water.走了很长的路我们才找到水.
We had sailed for two days before we saw the land.航行了两天我们才发现陆地.
It was midnight before my brother came home.我哥哥直到半夜才回来.
3.如果强调从句谓语动作未发生就发生主句谓语动作,只用before,这时常译为“未及（不等）……就……”
For example:
1）We can leave early in the morning before it gets too hot.趁天还不太热,我们上午早点离开.
2）I must write it down before I forget it.趁我还未忘,我必须把它记下来.
4.表示“与其说……倒不如……”,“与其……毋宁……”的意思时只用before.
For example:
I would give up my job before I agree to be dismissed.我与其被解雇还不如先辞职.
He will die of hunger before he steals.他宁愿饿死也不愿意去偷.
5．在某些特定句型中用before.
It was (not) long before…（不久）过了很长时间才…
It will (not) be long before…（不到）要过很长时间才会…
For example:
.It will probably not be long before they understand each other.
他们大概过不久就会互相了解.
It was not long before the whole country rose up.
不久全国人民奋起反抗.
三.下列情况一般使用until
1.主句是持续性谓语动词时,肯定,否定都可以,但意义完全不同,肯定表示动作终止,而否定表示动作开始.
For example:
1). We discussed the problem until/before he came back.
我们一直讨论到他回来.
2). We didn’t discuss the problem until he came back.
我们一直等到他回来才讨论问题.
2．Not…until…句型尽管在某些情况下可与before互换使用,但在强调句中一般仍用until;
1). It was not until he told me that I knew it.直到他告诉我我才知道这件事.
2）.It was not until he finished his homework that he went home.直到完成作业他才回家.
3）放于句首时用until.
For example:
Antil he finished his homework ,he didn’t go home. 直到完成作业他才回家.
应注意：在使用not until时,若not until放于句首,句子应部分倒装. For example:
Not until he finished his homework,did he go home. 直到完成作业他才回家
二、until与before的区别
　　1.可直接换用的情况:在until能使用的句型中,即主句含有否定式终止性谓语动词或肯定式延续性动词,可与before直接替换,意义差别不大.如:
　　①The students won't go home until / before they finish their homework.学生们要先完成作业才能回家.
　　②The woman worked in the factory until/before 1990. 1990年以前这妇女在这家工厂上班.
　　2.不可换用的情况:当主句含有肯定式终止性谓语动词时,只能用before不能用until,且before常意为"没来得及……"或"……才……"等.如:
　　③Einstein almost knocked me down before he saw me.爱因斯坦差不多将我撞倒才看见了我.
　　④He had measured me before I could get in a word.我还没来得及插话,他就把我的尺寸量好了.
　　三、not until的倒装与强调结构
　　1.当Not until位于句首时,句子要倒装.其结构为:Not until+从句/表时间的词+助动词+(主句)主语+谓语+.如:
　　①Not until the teacher came in did the students stop talking.直到老师进来学生们才停止讲话.
　　②Not until next week will the sports meet be held.直到下周才开运动会.
　　2. not until的强调结构为:It is / was not until+从句/表时间的词+that+.上面两句改为强调句为:
　　③It was not until the teacher came in that the students stopped talking.
　　④It is not until next week that the sports meet will be held.