a dog is being petted adog being petteda dog is being petted a dog being petted 区别不同
问题描述：
a dog is being petted adog being petted
a dog is being petted a dog being petted 区别不同
答
a dog is being petted.句子，一条狗正受到宠爱。
a dog being petted. 短语，一条正受到宠爱的狗。being petted现在分词短语，后置定语修饰dog。
答
前者：一只小狗正在被抚摸 （完整句子）
后者：一只正在被抚摸的小狗 （名词短语）
答
a dog is being petted 一条狗正在受到（主人的）宠爱.
a dog being petted 一条正在受到（主人的）宠爱的狗.