如图所示,有一束光线射入杯中,在杯底形成光斑,逐渐往杯中加水,光斑将( )
A:向右移动
B:向左移动
C:不动
D:无法判断
—The man at the gate _______ be our headmaster. He is always standing there every morning.
—No, it _______ be him. He is holding a meeting in the office now.
如图是“探究平面镜成像特点”的实验装置.透明玻璃板竖立在直尺上方,且底边与直尺相互垂直,两支相同的蜡烛A、B竖立在玻璃板两侧的直尺上,以蜡烛A为成像物体.