It’s really unwise of some teenagers from low-income families to spend a large sum of money on Apple products ______ they could buy other cheaper brands.

A．unless

B．when

C．so that

D．in case

运输过程中除了起点和终点以外还有一个或一个以上的经停点，该种运输方式是（）。

A．班线运输

B．单程运输

C．返程运输

D．中转运输