1. By comparison, relatively little is known about the internal structure of the earth.
    相形之下，对于地球内部结构则了解得较少。

2. Places that until recently were deaf and dumb are rapidly acquiring up-to-date telecommunications that will let them promote both internal and foreign investment.
    一些不久前还是信息闭塞的地方正在快速获得最新的通信技术，这将促进当地对国内外投资的吸纳。

3. I can send him a note via the internal mail system.
    我可以通过内部通讯系统给他发个通知.