用久的灯泡会发黑，是因为钨丝发生了下列哪种现象：[ ]
A.凝固
B.升华
C.凝华
D.先升华后凝华
答案：D
— Jake told me he was in the museum just now.
— He is actually at home.________, he’s upstairs doing his homework.
A．Believe it or not
B．In general
C．In your opinion
D．In the end
一个服装销售企业的10个分店某月的销售额(单位：万元)分别为：20 30 40 40 40 45 45 50 60 60，这10个分店销售额的众数为( )。
A．40
B．42.5
C．45
D．50
