不是代詞.是100%的疑問(wèn)副詞.
通常,你的老師總是告誡你,副詞前千萬(wàn)不要加任何介詞,這句話在多數(shù)時(shí)候是對(duì)的,但不總是對(duì)的.凡事皆有例外.
一般情況下,at/on/ to + adv.是錯(cuò)誤的.
但介詞from+ adv.是對(duì)的.
我們不可以說(shuō)：Where are you going to?
而說(shuō)：Where are you going?
但卻必須說(shuō)：Where are you from?(from where is right.)
再如,從國(guó)外回來(lái)：
come back / return from abroad (adv.)
但不可以說(shuō):study in abroad; go to abroad.