在反应3BrF3+5H2O====HBrO3+Br2+9HF+O2↑中，若有3 mol水作还原剂时，被水还原的BrF3的物质的量为（ ） A.3 mol B.2 mol
一When did you learn the news that Obama made a trip to Canada as President?一 was on my return． A．That B．It C．There D．This
If you _____ it , I will lend the book to you. A. read B. will read C. have read D. were reading
（·天津市耀华中学高三暑假验收考试） 5Jack must be worried about something．You can it from the look on his face． A．regard B．recognize
Our attitude toward our teachers should be _____, but not slavish or superstitious. A. respectable B. respected C. respective D. respectful
某单位要邀请10位教师中的6位参加一个会议，其中甲、乙两位教师不能同时参加，则邀请的不同方法有（ ）A.84种 B.98种
While watching TV, . A. the doorbell rang B. the doorbell rings C. we heard the doorbell ring D. we heard the doorbell rung
在多细胞生物体内，细胞并没有表现出全能性，这是因为 A． 由于细胞分化而丧失了全能性 B、细胞内的基因表达有特定的时空选择性 C
x=2sin45°-1 
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解析: