已知一组数据1，a，3，6，7，它的平均数是4，这组数据的众数是（ ）。
3
— There used to be many trees in the city.
— Yes, but there are _______ now. [ ]
A. less
B. few
C. a few
D. fewer
人感染旋毛虫的方式是通过（）
A.皮肤
B.呼吸道
C.血液
D.密切接触
E.饮食
