若幂函数f(x)=xk在(0,+∞)上是减函数,则k可能是( )
A:1
B:2
C:12
D:-1
如图,在直角坐标系中,A(﹣1,5),B(﹣3,0),C(﹣4,3).
(1)在图中作出△ABC关于y轴对称的图形△A1B1C1.
(2)写出点C1的坐标.
Reading her biography, I was lost in admiration for _______ Doris Lessing had achieved in literature.
①加快高山冰川的融化速度
②推广滴灌技术
③修建水库
④实施跨流域调水工程
⑤大量抽取地下水来缓解旱情