Look,____people are walking in the street.英语选择题

Look,____people are walking in the street.英语选择题
（ ）Look,____people are walking in the street.
A.a lot
B.an ocean
C.an ocean of
D.ocean of
选哪个?
我觉得没有正确答案.
应该写的是oceans of.
各位英语高手帮忙看一看.