【单选题】Thirteen and eighteen is _____________. [ ]
【简答题】A.About four thirty. B.About five thirty. C.About three thirty. D.About three,
【简答题】影响反应速率的因素主要有 、 、 、 四种。
【简答题】影响化学反应速率的因素主要有 、 和 。
【单选题】I have ___________ pencil-cases. [ ]
【单选题】Twenty-one plus sixteen equals . [ ]
【单选题】I usually exercise __________.
【单选题】He played golf _____. [ ]
【单选题】There are _____ boys in my class. [ ]