水刷石喷刷。冲洗是确保水刷石质量的______之一，冲洗不净会使水刷石表面______或明暗不一致。
参考答案：重要环节；颜色发暗
Ben is one of ________ students in our class. He keeps doing sports every day.
A．strong
B．stronger
C．strongest
D．the strongest
