There must be a dog sitting behind it .为什么sit 后面加ing

There must be a dog sitting behind it .为什么sit 后面加ing There Must Be A Reason 歌词 there must be a use for my -What is behind the door? -There must be a dog sitting behind it. sitting behind it,为什么是sitting?而不是sit 或sat? must后必须跟be吗?It must be a dog是正确的 It must is a dog是错的吧 I think there will be a dog!反意疑问句 There must be a reason.可以用There must is a reason. 英语作文There must be a use for my talent There must be something wrong. __that a dog over there? __that a dog over there? there must have been a storm there.__.a there couldn't be b.I think there was ______ there a little dog ____ on the corner of the street ,lisa ----- no(be) (lie) Be careful!There is a dog in front of us改为同义句 There must be a man waiting for you in the distance.为什么“There must be”,我认为,这样的话应该是the man,因为这样才有特指,才会must There must be a man waiting for you in the distance.为什么“There must be”,我认为,这样的话应该是the man,因为这样才有特指,才会must there might be a big dog ____ there.A sit B sat C sitting 选C 为什么 sitting前不加is The ____ of the dog must be worrde