雕品“百花争艳”属于（）。
A.整雕
B.零雕整装
C.浮雕
D.镂空雕
参考答案：B
已知关于x的方程x2-（a2-2a-15）x+a-1=0两个根是互为相反数，则a的值为______．
Although we are young, ______ we can still do something to help them.
A．but
B．/
C．and
D．however
