Metro 1000支持的安装方式有（）
A.壁挂
B.桌面
C.开放式机架
D.ETSI机架
参考答案：A, B, C, D
设f（x）=ax2+bx，1≤f（-1）≤2，2≤f（1）≤4．求f（-2）的取值范围．
My friend likes singing and talking with others. But I often stay at home to watch TV. So my friend is than me.
A． seriouser
B．more serious
C．calmer
D．more outgoing
