They went to Rome by ship.
They went to Rome by car.
They walked to Rome.
They flew to Rome.
《几点吃饭？》中可知：他们坐飞机去罗马。
A选项“他们坐船去罗马”，B选项“他们坐汽车去罗马”，C选项“他们走路去罗马”均不符合题干要求，故选D选项。
