五种类型：
一、利弊分析（手机的使用、网购、电子课本、网上交友、请家教）
结构：
Part1: As we all know，… is becoming more and more…,different people have different opinions on it/every coin has two sides.
Part2: The advantages of it are(on the one hand)…First of all… what’s more… besides… last but not least….. The disadvantages of it are(on the other hand )…To begin with,… next… finally…
Part3: In my opinion， …= To my mind， …= As far as I am concerned， …= I am of the opinion that in short; briefly/ in brief ; generally speaking, in a word,
