语法与词汇 32.Once they had______that he was not a spy, they agreed to release him.
【正确答案】 A
【答案解析】这句话的意思是:一旦确认他并非间谍,他们就同意将他释放。ascertain意为“确定、查明”;ascribe意为“归因于、归咎于”:avert意为“防止、转移”;assert意为“断言、主张”。根据句意,选项A为正确答案。