【正文】 about…。例如：　　It is nice talking to you. 跟你交談真是愉快。but并列了the brain后的兩個謂語finds it inefficient to keep…和 can create new receptors if necessary。(2007Text2)　　【結構分析】本句中It為形式主語，真正主語是其后how引導的主語從句，how the capacity suits one to answer questions，兩個不定式結構to…作capacity的后置定語， questions后面的that引導定語從句，關系代詞that在從句中作主語。 “it”并無實際意義。在我們證實這件事之前可以向大氣中不斷地排放氣體。s no good /use doing that. 那樣做沒好處(沒用)。這時，it也無實際意義?！　±?：Further more，it is obvious that the strength of a country’s economy is directly bound up with the efficiency of its agriculture and industry, and that this in turn rests upon the efforts of scientists and technologists of all kinds. (200072)　　【結構分析】本句主干為it is obvious that…，其中it是