30.若超音波脈衝時間長度(pulseduration)為1μs ,且其責任因子(duty factor)為0.008 ,則脈衝重複週期 (pulse repetition period )為多少μs ?
(A)100
(B)125
(C)250
(D)800
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統計: A(16), B(1908), C(65), D(215), E(0) #2407849
統計: A(16), B(1908), C(65), D(215), E(0) #2407849