如图所示是一种天文望远镜的光路图，分析图中光路可知它的物镜是（）

Mr. Norman has raised some interesting points, but there’s one thing he has completely failed to ____________________.

下列转化关系不能通过一步反应直接完成的是（   ）

能形成珍珠的结构是（）

A giant helium（氦） balloon is telling residents of Paris how good or bad the air quality is．When it’s good, the balloon ----measuring 22 meters wide and 32 meters high---shines green．_________, it’s red．