下列不属于无土栽培优点的是（）

根据下文回答问题。

      我们的人生旅程就像大海一样，时而惊涛骇浪：浪潮冲击礁石，呈现出一种雄浑；时而安静沉寂：____________________，____________________。使我们能够记住的，也许不是那无比深邃气吞日月的气势，而很可能是一朵细小的浪花，记住它的原因也很简单，那就是它带给我们平和的舒适感。

      Many people like to travel by plane, but I don't like it because an airport is usually far from the city. You have to get there early and wait for hours for the plane to take off and it is often late. You can't open the windows. You can't choose the food. Planes are fast, but it still takes hours to go out of the airport and into the city.

      I like traveling by train. I think trains are safe. Railway stations are usually in cities. When you are late for a train, you can catch another one. You can walk around in the train and open the windows. You can see many interesting things on your way. I know it takes a little more time.

      I also like cars. You can start your journey when you want to and you don't need to get to a railway station or a bus stop. Also you can carry many things with you in a car. But sometimes there are too many cars on the road.