【题目】Comparison may make something appear more beautiful than it is when _____ alone．
A. seen B. seeing C. see D. to see
在线课程【答案】A
【解析】Appear+形容词，好像……的。比较从句为：比单个被看时它是漂亮的（than it is beautiful when it is seen alone），由于重复，省略了表语和时间从句的主语谓语。因此该句主句与谓语构成被动关系，选过去分词，seen。