答案是surrunded,既然是被动语态,为何没有be的形式
They live in a beautiful white house surrounded by green trees.这一句中 surrounded by green trees 是一个省略性的定语从句,来修饰先行词house,他们住在一间什么样的house?一个被绿树环绕的house,这个句子完整的形式是:They live in a beautiful white house (which is ) surrounded by green trees.