您的问题很简单.百度知道很高兴帮助您解决您提出的问题.
原句：There is a tree in front of our classroom
翻译：我们教室前面有一棵树.
否定句：我们教室前面没有一棵树.：We are not a tree in front of the classroom
否定句：我们教室前面一棵树也没有.：We also have no a tree in front of the classroom
百度知道永远给您最专业的英语翻译.