《What Are You Doing?》Going to Beijing PPT
《What Are You Doing?》Going to Beijing PPT第5页

主语在句首,am,is,are 跟在后, 现在分词跟着走,其他成分不可丢。 表示动作正进行,句中now 时间定。 变为一般疑问句,把be 提到句首去。 否定句式也简单,be 后只把not 添。

Look! Some birds __________ in the sky. A. fly B. is flying C. are flying