— Will you be         this afternoon, John?

— I am afraid not. I have an appointment with my dentist.

A．convenient

B．suitable

C．accurate

D．available

孔子登东山而小鲁，登泰山而小天下；刘勰“登山则情满于山”；杜甫则“会当凌绝顶，一览众山小”……

请以“登上高山”为话题，写一篇不少于800字的作文。文体不限，题目自拟。