If you educate the public about dangerous diseases they can protect themselves, which will help to halt the spread.
如果你能教育公众如何来防治危险疾病,他们就能够保护好他们自己,从而阻止疾病的传播。
and assuming such an automatic messenger picked up our first broadcasts of the 1920's,
假定外星人的这种自动化信息装置接收到了我们二十世纪二十年代的第一次广播信号,