On a certain transatlantic crossing, 20 percent of a ship’s passengers held round-trip tickets and also took their cars abroad the ship.  If 60 percent of the passengers with round-trip tickets did not take their cars abroad the ship, what percent of the ship’s passengers held round-trip tickets? C

A.     33 %

B.     40%

C.     50%

D.     60%

E.      66 %

设passengers with round-trip tickets为X.

(X*0.4)/0.2=1

X=1/2