這句話的結(jié)構(gòu)分析如下：it：形式主語considering ...and introducing...：整段是真正的主語what makes "convenience" foods so popular：是considering的賓語從句一般來說,it作形式主語有3種方式：1） 代替不定式作...我知道it is worth while doing sth。但it is worth doing,doing是真正主語是第一次見到。你肯定嗎？It is worth reading a book是正確的？= Reading a book is worth.?在現(xiàn)代英語中，在be worth前使用形式主語it被認(rèn)為是合習(xí)慣的。it is worth doing sth.是很正常的說法。例如以下國外原聲例句：It is worth locking these tickets in early and getting a refund later if your plans change. （BBC: Insider flight tips from a seasoned business traveller）worthwhile的意思大致和worth一樣，但其后可接動(dòng)名詞或不定式It is worthwhile doing sth.It is worthwhile to do sth.但worth后面只能接動(dòng)名詞。而且，若不用形式主語it而直接用動(dòng)名詞作主語則是錯(cuò)誤的，雖然it是代表動(dòng)名詞作主語。如：正：It is worth reading a book. 誤：Reading a book is worth.明白。但這里的it顯然不是形式主語，因?yàn)橥耆贿m合形式主語（可替換）的規(guī)則。我也找到了一些例句。It is worth remembering that before the 20th century, all the arts were interactive.值得一提的是，在20世紀(jì)以前，所有的藝術(shù)都是互動(dòng)的。In conclusion, it is worth remembering what a treasure trove these tapes truly are. （BBC: The Jackie Kennedy tapes: Sharp, tender and gossipy）Thanks.