把一个句子改成同义句.
问题描述：
把一个句子改成同义句.
There were many green trees in this area in the past.
There __ __ __many green trees in this area in the past.
答
used to be
把一个句子改成同义句.
There were many green trees in this area in the past.
There __ __ __many green trees in this area in the past.
used to be