The London fire in 1644 lasted three months ( ) it died out.

answer B
until和before的区别：
until/not until是指：直到什么时候为止...其中非延续性动词用后者，延续性动词用前者。
例句：Not until my father came back did I fell asleep.
I was awake until my father came back.
注意：倒装时倒装主句，从句语序不变。改为强调句时基本语序不变。

before在...之前，常用在时间状语从句中。
常用句型：It is +( )+before...
注意：前后时态要一致，遵从主将从现原则。
翻译：1...就...It was not long before he turned against his country.不久他就背叛了他的祖国。

A

B
选A的话应该是The London fire in 1644 has lasted three months before it died out.

B,意为一直到