Because of the rising cost of fuel, scientists are building automobile engines who will conserve gasoline but still run smoothly.
  • 1、
【正确答案】 1、正确答案：who--that／which    
【答案解析】解析：考查定语从句的引导词。定语从句的先行词engines是物而不是人，指代先行词的引导词不能用who，而应改为that或which。