There is a pencil on the desk?（改为一般疑问句并作肯定回答）

Is there a pencil on the desk?
Yes,there is.Is there a dictionary on the teacher‘s desk？（改为复数句子）Are there dictionaries on the teacher's desk?The gym is behind the science lab.（改为同义句）The science lab is before the gym.The science lab is in front of the gym.