截至到2008年底，安徽全省总人口6740.8万，占全国人口5.08%，居全国第_____位。
A．七
B．八
C．九
D．十
参考答案：B
Monkeys in the zoo have shown the flu ______ since last Monday and altogether 20 have died until now. [ ]
A. symbol
B. sign
C. signal
D. symptom
已知C是以AB为直径的⊙O上一点，过点C作⊙O的切线交直线AB于点D，则当△ACD为等腰三角形时，∠ACD的度数为______．
