Look at the duck buidling.It was a duckling.为什么不用“it is”?

Look at the duck buidling.It was a duckling.为什么不用“it is”? Let's go and have look the duck找错误 Look!The duck is hungrily.这句话是不是病句?快, Look At The Sky look at the boy. look at the Look at the picture Look at the 造句 look at the look at the chart look out at the look at the beach Look at the blackboard look at the Look at the look at the ( ),please LOOK AT THE STARS Look at the ears!