VOA慢速英语:Vaccine-Autism Study Is Withdrawn

eight of them指的是eight of the twelve children，这种方法也可以用来表达分数，例如eight of twelve,eight out of twelve.
shortly after……之后不久，after receiving the vaccine是现在分词作状语。

2.Opening and closing it changes the temperature too much.

动名词做主语

动名词作主语，倾向于陈述一个既定事实。比方说：sleeping is necessary.睡眠是必要的。
schooling costs a family a lot.上学花费家庭许多钱。

但是不定式作主语，倾向一个因果关系、逻辑关系。比方说：to say goodbye to all of you my friends is hard for me.要对你们，我所有的朋友说出再见不是一件容易的事。
to waste other's time means chronic murder.浪费别人的时间就是慢性谋杀。

3.Vaccines should also be kept away from the walls of the refrigerator and out of the "crisper" drawers usually found at the bottom.

keep away from(使)不接近

例句：Keep away from the furnace.
      不要靠近炉子。

      Keep the children away from the machine.
      别让孩子们接近机器。

避开

例句：As long as you can keep away from them, you're safe.
      只要你离他们远一点, 你就会安全。

      He keeps away from liquor and tobacco.
      他不喝酒, 不抽烟。