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【单选题】
Company Alpha buys free-travel coupons from people who are awarded the coupons by Bravo Airlines for flying frequently on Bravo airplanes. The coupons are sold to people who pay less for the coupons than they would pay by purchasing tickets from Bravo. This marketing of coupons results in lost revenue for Bravo. To discourage the buying and selling of free-travel coupons, it would be best for Bravo Airlines to restrict theA.
number of coupons that a person can be awarded in a particular year.
B.
use of the coupons to those who were awarded the coupons and members of their immediate families.
C.
days that the coupons can be used to Monday through Friday.
D.
amount of time that the coupons can be used after they are issued.
E.
number of routes on which travelers can use the coupons.
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【简答题】苯酚及其衍生物具有致癌、致畸、致突变的潜在生物毒性,在许多国家,苯酚已被环保部门列入优先控制污染物,其生物降解法具有经济高效、无二次污染等优点。利用万方数据库,检索2016-2018年,题目中含“苯酚降解菌”的期刊论文、学位论文,会议论文及专利,共检索到___条结果,其中期刊论文___篇,学位论文___篇,会议论文___篇,专利___篇,所属专利类型主要是___。
【判断题】(1)金属凝固时,过冷度越大,晶体长大速度越大,因而其晶粒粗大。( ) ( 2 )无限固溶体必是置换固溶体。( ) ( 3 )间隙固溶体的溶质原子直径小,其强化效果远比置换固溶体差。( ) ( 4 )凡二元合金从液相结晶成固相后, 晶体结构便不再改变。( )
A.
正确
B.
错误
【单选题】如图所示,已知z 1 =24, z 2 =28, z 3 =36, z 4 =20, z 5 =80, z 6 =24, z 7 =32, z 8 =24, z 9 =36,i 19 = ( )。
A.
3
B.
6
C.
9
D.
12
【简答题】一轮系如图所示。已知电机转速n 1 =1000r/min，z 4 =4z 1 ，z 6 =2z 5 ，z 7 =z 8 ，z 9 =1，z 10 =100，齿条z 11 =20，m=4mm。求齿条的速度及方向。
【简答题】置换固溶体必是无限固溶体。
【简答题】无限固溶体必是置换固溶体。
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