原文有錯(cuò).應(yīng)該是“But my mom does.”
原文中應(yīng)該有上文,比如：My dad doesn't like shopping.But my mom does.意思就是：我爸不喜歡逛街購物,但是我媽喜歡.
Does（或者do或者did）所代表的意思就是上句中的動(dòng)詞（不能是系動(dòng)詞或能愿動(dòng)詞,只能是動(dòng)作動(dòng)詞）,而且上句應(yīng)當(dāng)是個(gè)否定句.
與之相似的例子有：
（1）I don't smoke.But my younger brother does.我不抽煙,但是我弟弟抽.
（2）The gray dress doesn't have a pocket.But the blue one does.這條灰色的裙子沒有口袋,但是那條藍(lán)色的有.
（3）My dad doesn't wear glasses but I do.我爸爸不戴眼鏡,但是我戴.
（4）I didn't buy anything.But he did.我什么也沒買,但是他買了.
當(dāng)上句里面的動(dòng)詞是系動(dòng)詞或者能愿動(dòng)詞的時(shí)候,下句里就不用does來代替了,而用該系動(dòng)詞或者能愿動(dòng)詞.但是結(jié)構(gòu)都是一樣的.
例如：
（1）I'm not British but he is.我不是英國(guó)人,但是他是.
（2）I can't swim but she can.我不會(huì)游泳,但是她會(huì).
（3）Jack shouldn't pay for it but you should.Jack不應(yīng)該付錢,但是你應(yīng)該.