直线l：y=kx+1与圆O：x²+y²=1相交于A，B 两点，则“k=1”是“△OAB的面积为$\frac{1}{2}$”的（　　）

社会公共秩序的维护主要应靠（    ）

俄国教育家乌申斯基说：“良好习惯乃是人在神经系统中存放的道德资本，这个资本在不断增值，而人在其整个一生中就享受着它的利息。”这句话主要告诉我们（  ）

    Hello! I'm Victor.I have a bed, a desk, two chairs and a computer in my bedroom.My bed is small but very nice.It's blue because I like blue very much.My desk is big.It's white.You can see a computer and so many books on it.I do my homework here.I have two chairs.One is big and one is small.The big one is near the bed.The small one is near the window.I like my room.