【单选题】
A <{p}><{font _mstmutation="1" _msttexthash="7745361" _msthash="475"}>.τ;<{/font}><{br/}><{/p}>
B <{p}><{font _mstmutation="1" _msttexthash="8705164" _msthash="351"}>.ατ;<{/font}><{br/}><{/p}>
C <{p}><{font _mstmutation="1" _msttexthash="12199330" _msthash="523"}>(1-α3)τ;<{/font}><{br/}><{/p}>
D <{p data-we-empty-p="" _msttexthash="313599" _msthash="307"}>(1-α4)τ<{/p}>
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