Our classroom ______ every day. We can study comfortably in it.
A:clean
B:cleans
C:is cleaned
D:was cleaned
如图,已知l1∥l2∥l3,相邻两条平行直线间的距离相等,若等腰直角△ABC的三个顶点分别在这三条平行直线上,则sinα的值是( )