现在进行时
表示说话时正在进行的动作或现阶段一直在进行的动作。
☆注意☆它的构成是：be的现在时形式（am , is , are）加动词的ing形式。
如：What are you doing? I’m writing a letter. What arethey doing? They’re swimming.Is he playing chess? Yes, he is.Look, Amy is reading an English book.
☆ 注意☆ 动词的ing形式的构成规则：
☆ ① 一般的直接在后面加上ing , 如doing , going , working , singing , eating
② 以e 结尾的动词，要先去e再加ing ，如having , writing
③ 双写最后一个字母的（此类动词极少）有：running , swimming, sitting , getting
