如图：在等腰△ABC中,AB=AC，AD上BC，垂足为D，以AD为直径作⊙O，⊙O分别交AB、AC于E、F.
下列气体中能形成酸雨的是（ ）
You go to see a doctor in a hospital. When he asks you, “What’s your trouble?” You should say “ . ”
