____in the United States,St.Louis has now become the 24th largest city.A being the fourth biggest cityB it was once the fourth biggest cityC once the fourth biggest cityD the fourth biggest city it was
问题描述：
____in the United States,St.Louis has now become the 24th largest city.
A being the fourth biggest city
B it was once the fourth biggest city
C once the fourth biggest city
D the fourth biggest city it was
答
曾经是美国第四大城市的圣·路易斯，现在是第二十四大城市。
这道题能做出来主要靠的是语感。
答
once the fourth biggest city in the united States,St,Louis has now become the 24th largest city.
曾经是美国第四大城市的圣路易司如今已经成为第24大的城市。
once adv.曾经 后句可看出有变化之意，因此前句应说过去怎样，故选C
答
C
前面那个是不能有动词的,因为他是从句.所以可以选A,C
但是他后面又说圣路易斯变成了第24大城市,那就是说他 以前 是第四大,所以要用once而不是being
答
once 连词 曾经
省略了主谓语,完整应该是
Once it was the fourth biggest city,