【简答题】(8分)已知:CH 3 CH 2 OH+NaBr+H 2 SO 4 (浓) CH 3 CH 2 Br+NaHSO 4 +H 2 O。 实验室制备溴乙烷(沸点为38.4℃)的装置和步骤如下: ①按右图所示连接仪器,检查装置的气密性,然后向U形管和大烧杯里加入冰水;②在圆底烧瓶中加入10mL95%乙醇、28mL浓硫酸,然后加入研细的13g溴化钠和几粒碎瓷片;③小火加热,使其充分反应。 试回答下列问题:...
【简答题】EPON系统采用( )技术,实现( )传输。
【单选题】----She has two best friends. ----__of them is in the country.
【单选题】一She has two best friends.一___of them is in the country.
【简答题】She has been given three free tickets for tomorrow’s concert and she ______ there with two of her best friends. A.has gone B.is going C.has been D.went
【判断题】钱钟书先生《宋诗选注》认为:苏轼为“中国古代田园诗的集大成”者。晚年,于石湖所作《四时田园杂兴》(60首)是其代表作。
【简答题】She has two best friends. _____of them is in the country. A: Both B; All C; Neither
【判断题】EPON系统采用WDM技术,实现单纤双向传输