But a lot of problems are coming about. Traffic in cities is getting heavier and heavier. The car is causing more pollution. To solve these problems, something must be done.

　　此篇書(shū)面表達(dá)的中心“轎車(chē)進(jìn)入家庭后所產(chǎn)生的影響”，由兩個(gè)主題句 It has advantages 和 A lot of problems are coming about 體現(xiàn)出來(lái)。為了進(jìn)一步展開(kāi)主題句 It has advantages，文章從convenience, saving time and developing car industry and economy 三方面加以論證;為了展開(kāi)主題句 A lot of problems are coming about，文章從 traffic 和 pollution 兩方面加以說(shuō)明。這樣利用主題句使文章層層相扣，形不散，神也不散，文章讀起來(lái)朗朗上口，生動(dòng)有趣。