Ⅰ. at the top of “在……顶点上、在……上”。At 表示点，在句子中用作状语，反义短语常为 at the bottom of “在……底部”;
on (the) top of 中的on 表示部位上的接触，意思是“在……之上、在……上面”。反义短语常为at the foot of “在……脚底下”。如：
① He shouted at the top of his voice. 他高声地叫喊。
② He is at the top of the class.他居全班之首位。
③ Will you please put this box on (the) top of the books.请你这个盒子放在那些书的上面好吗?