单根牙以_______处的牙周膜面积最大，多根牙以_______处的牙周膜面积最大，_______次之。
参考答案：牙颈部；根分叉区；牙颈部
The most popular store is at the end of the street. [ ]
A. clothing
B. clothes
C. cloth
D. A and B
Paul is Year 6 Star School in Shanghai.[ ]
A. in; on
B. at; in
C. at; at
D. in; at
