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【单选题】
f1(t)=δ(t+1)-δ(t-1),f2(t)=cos(ωt),则f1(t)*f2(t)=A.
cos(ωt)+cos(ωt-1)
B.
cos[ω(t+1)]-cos[ω(t-1)]
C.
cos[ω(t-1)]-cos[ω(t+1)]
D.
cos[ωt+1)]-cos[ω(t-1)]
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举一反三
【单选题】All of our export dangerous cargo is ______ examined before shipment．
A.
Though
B.
Through
C.
Thorough
D.
Thoroughly
【单选题】Symmetric cleavage of β-carotene yields _____ molecules of all- trans -retinal, which can be either further oxidized to all- trans -retinoic acid, or reduced to all- trans -retinol, vitamin A 1 .
A.
1
B.
2
C.
3
D.
4
【单选题】All of our export cargo is ________ examined before shipment
A.
though
B.
thoroughly
C.
through
D.
throughout
【单选题】The statement calls for a removal of all trade barriers for the export of _________.
A.
the Commonwealth
B.
industrialized countries
C.
less developed countries
D.
all the nations
【简答题】用莫尔法测定溶液中Cl-含量,下列说法正确的是()。A. 标准滴定溶液是AgNO3溶液 B. 指示剂为铬酸钾 C. AgCl的溶解度比Ag2CrO4的溶解度小,因而终点时Ag2CrO4(砖红色)转变为AgC1(色) D. n(Cl-)=n(Ag+)
【多选题】用莫尔法测定溶液中C1-含量,下列说法正确的是()
A.
标准滴定溶液是AgNO3溶液
B.
指示剂为铬酸钾
C.
AgCl的溶解度比Ag2CrO4的溶解度小,因而终点时Ag2CrO4(砖红色)转变为AgCl(白色)
D.
n(Cl-)=n(Ag+)
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