在Windows XP中，“显示”图标是在（）中。 ["开始菜单","控制面板","任务栏","工具栏"]
锦葵科的主要特征之一是具单体雄蕊。单体雄蕊特点是（） ["仅为一个雄蕊","多个雄蕊，仅一个离生","所有雄蕊的花药合生，花丝分离","所有雄蕊的花丝连合成管，花丝顶端及花药离生","所有雄蕊的花丝、花药连合成一管状物"]
Although lube oils used in the main lubricating service systems should have a relatively high flash point to avoid ignition, they can create smoke and fire hazards when they （）. ["are exposed to a vacuum","come in contact with extremely hot surfaces","are reduced in temperature to just above the pour point","become extremely agitated or aerated"]
天然气相对密度在（）以上称为湿气。 ["0.8","1.0","1.5","1.6"]
光滤波器
简述供暖系统按供热范围的分类。
