空气洁净度是指洁净环境中空气含( )的程度。
A．二氧化硫
B．有害气体
C．尘埃量
D．细菌
参考答案：C
Generally speaking, _____ graduate from _____ famous university is more likely to find a job. [ ]
A. a; a
B. /; the
C. the; a
D. the; the
差热曲线中起点和终点各代表什么意义？
