状语从句
状语是用来修饰动、形、副词的句子成分。由副词，介词短语，分词，分词短语，不定式，从句来充当。可以表示地点，时间（伴随），原因，目的，结果，条件，让步，程度，方式，比较。位置可在句首、中、末。
状语从句---------
●时间状语从句：when, while, as, before, after, since, till, until, by the time, as soon as,
once,
immediately, directly, instantly, the moment, the minute, the time, the day, each time, every time, any time, on doing sth, on one’s+ noun., no sooner…than, hardly…when, scarcely…when,
●地点状语从句：where, wherever,
●原因状语从句：because, since, as, now(that), seeing that, considering that, in that, for, ●目的状语从句：so, so that, in order that, in case, for fear that, lest
●结果状语从句：so, so…that…, such…that…
●条件状语从句：if, unless, as long as, so long as, in case, if only
●方式状语从句：as, (just) as…so, as if / as though
●让步状语从句：though, although, as, even if, even though, whether, while, whoever,
whatever, whichever, whenever, wherever, however, no matter who/ what/ which/ when/ where/ how,
