If you can make us a firm offer at a ______ price, we will place an order with yourcorporation.
A. competitive
B. comparative
C. subjective
D. objective
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We should be pleased to send you some samples of our new typewriter on approval, ______ our own expense.
A. at
B. on
C. for
D. in
一般物质的荧光效率范围是( )
A. 0-0.1
B. 0- 0.5
C. 0-1
D. 0-2
化合物的共轭度越大，荧光效率越（ ），荧光波长（ ）移。
A. 大，蓝
B. 大，红
C. 小，蓝
D. 小，红
溶液荧光强度与荧光物质的浓度呈线性关系时，Ecl满足条件是（）
A. ＞0. 1
B. ≤0.1
C. ＞0.05
D. ≤0.05
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