下列不属于单细胞生物的是( )
A:变形虫
B:草履虫
C:衣藻
D:病毒
—How many times _______ you _______ to Beijing this year?
—Three times.
如图,在平面直角坐标系中,△ABC的边AB∥x轴,点A在双曲线y=5x(x<0)上,点B在双曲线y=kx(x>0)上,边AC中点D在x轴上,△ABC的面积为8,则k= ____.