下列反应中属于取代反应的是 ① CH3CH＝CH2＋Br2CH3CHBrCH2Br② CH3CH2OHCH2＝CH2＋H2O③ CH3COOH＋CH3CH2OHCH3COOCH2CH3＋H2O④ C6H6＋HNO3C6H5NO2＋H2OA．①② B．③
室温下，水的电离达到平衡：H2OH＋＋OH－。下列叙述正确的是( ) A．将水加热，平衡向正反应方向移动，KW不变 B．向水中加入少量盐酸，平衡向逆反应
2010年1月2日起，我国北方大部地区遭遇大范围降雪天气袭击。大雪严重影响了民航、铁路和高速公路等交通，如图所示。在遇到这种天气时，为了尽快
Eliza remembers everything exactly as if it________yesterday. A．was happening B．happens C．has happened
下列函数中，周期为，且在上为减函数的是 A. B. C. D.
Fitness First Initiative for Teenagers（FFIT）is a plan from Fitness First in Australia．It provides FREE fitness to 14-18 year olds through its program FFIT Holidays． FFIT aims to encourage youn
Now then, children, Its time you ________. A. were washed and dressed B. washed and dressed C. are washed and dreesed D. washed and dress
3．依次填入下面一段文字横线处的语句，衔接最恰当的一组是（ ） 茫茫沙漠，滔滔流水，于世无奇。惟有大漠中如此一湾，风沙中如此一静
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