资源的有限性称为()的稀缺性。
A、消费
B、物质
C、需求
D、资源
参考答案：D
As young adults, it is our _____ to try our best to deal with each challenge in our education with the help of our teacher.[ ]
A. work
B. job
C. duty
D. task
CPITN的检查项目不包括（）
A.牙龈出血
B.牙结石
C.早期牙周炎
D.晚期牙周炎
E.牙槽骨吸收
