重点讲解：
1. drop off
中途放下（某人）；中途卸下（某物）；
eg. He was dropping off a late birthday present.
他正在送一份迟到的生日礼物。
eg. You can go there and drop off your things.
你可以到那里把你的东西放下。
2. protect against
保护；防护；
eg. A long thin wool coat and a purple headscarf protected her against the wind.
一件薄薄的羊毛长外套和一条紫色的头巾为她挡了风。
eg. Many foods contain substances that protect against tissue damage.
很多食物含有保护肌肉组织免遭破坏的成分，
3. be designed to do sth.
目的，旨在于；
eg. The course is designed to help students with colour and composition.
设置这门课程是为了指导学生如何运用色彩和构图。
eg. The roof has been ingeniously designed to provide solar heating.
房顶经过巧妙设计，可提供太阳能取暖。