语法填空
1. (2017·全国卷Ⅱ)In 1863 the first underground passenger railway in the world opened in London. It ran for just under seven kilometers and allowed people to avoid terrible crowds (crowd) on the roads above as they travelled to and from work.
2. (2017·全国卷Ⅱ)Later, engineers managed to construct railways in a system of deep tunnels(隧道), which became known as the Tube. This development was only possible with the introduction (introduce) of electric-powered engines and lifts.
3. (2017·全国卷Ⅰ) This trend, which was started by the medical community(医学界) as a method of fighting heart disease, has had some unintended side effects (effect) such as overweight and heart disease—the very thing the medical community was trying to fight.
4. (2018·全国卷Ⅲ) My name is Mireya Mayor. I’m a scientist (science) who studies animals such as apes and monkeys.
