【单选题】How long have the people known each other?
【单选题】听力原文:W: How long have you known Susan? M: I've known her about three years. I met her in the library where we used to read, but now I can only see her on the campus occasionally. Where did Susan often...
【单选题】______ have you known the city? For five years. [ ]
【简答题】在包有二层相同厚度保温材料的圆形管道上,应该将______材料包在内层,其原因是______,______。
【单选题】决 定化学反应速率的主要因素是反应物的性质,影响反应速率的因素有 、 、 温度、催化剂等.