and ,but ,so ,although ,though ,however 用法的区别,哪些要加逗号的?
例句：
I drank the beer ______ I didn’t want it.
I didn’t want the beer ,______I drank it.
I didn’t want the beer.I drank it,______.
I didn’t want the beer.______ ,I drank it.
I didn’t want the beer ,______I didn’t drink it.
I wanted the beer ______ I drank it.
注意标点的变化。
（只能用一次）