《中图法》在社会科学部类下展开为9个大类，自然科学部类下展开为（）大类。
参考答案：10个
There is ______ on the playground. [ ]
A. a groups of peoples
B. a group of people
C. groups of people
D. group of people
标准化水平高，便于统计、分析和比较的访谈是
A．集体访谈
B．纵向型访谈
C．非结构性访谈
D．结构性访谈
