分类：教育/科学-学习帮助
问题：作业求助英语单选___intheUSA,st.louishasn 
___in the U ,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
回答：A
现在分词做伴随状语。此为非谓语动词的用法。