六级But all these concepts are massively expensive, require safety certification standards for road and air, need dual controls, involve complex folding wings and propellers,and have to be flown from air-strips.

但所有这些概念都非常昂贵，需要道路和空气的安全认证标准，需要双重控制，涉及复杂的折叠机翼和螺旋桨，并且必须从气带飞行。

2019年6月六级真题（第二套）阅读 Section A

六级More than drones dropping a new supply of underwear on your doorstep, Apple's massively successful brick-and-mortar-and-glass retail stores and Amazon's small steps in the same direction are what should keep old-fashioned retailers awake at night.

不仅仅是无人驾驶飞机在你家门口扔下新的内衣，苹果巨大成功的实体和玻璃零售店以及亚马逊朝着同一方向迈出的小步应该让老式零售商在晚上保持清醒。

2019年6月六级真题（第一套）阅读 Section B

四级Have they become somehow massively more expensive to educate?

他们是否在某种程度上变得更昂贵了？

2013年12月大学英语四级考试真题(第3套)