What colour ?[ ]
A. is it
B. it is
答案：A
—Is the H1N1 flu (流感) very serious now?
—No, I don't think so. However, we _______ need to be careful with it.[ ]
A. Also
B. neither
C. still
D. don't
等比数列{an}中，a3=4，a7=16，则a5=[ ]
A．8
B．12
C．8或-8
D．12或-12
