40. Most airline companies request that every passenger _____ his or her cellphone before takeoff.
(A) turn off
(B) turns off
(C) to turn off
(D) turning off
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統計: A(273), B(102), C(84), D(42), E(0) #3154141
統計: A(273), B(102), C(84), D(42), E(0) #3154141