Yesterday is cooler than today.
Helen is thinner than Joan.
That black shirt is smaller than this blue shirt.
可以讲解一下么？
可以。
This is the cleanest room i have ever seen. (that room, dirty) That room is dirtier than this room.这是我曾经看到的最干净的屋子。那屋子比这间屋子脏。由于要求仿照例句，所以这里要变成比较级，以下同。
Today is the hottest day in the month. (Yesterday, cool) Yesterday is cooler than today.今天是这个月最热的一天。昨天比今天凉爽。
Joan is the fattest girl in the class. (Helen, thin)Helen is thinner than Joan.琼是班里最胖的女孩。海伦比琼瘦。
This blue shirt is the biggest in the shop.(that black shirt,small)That black shirt is smaller than this blue shirt.那件蓝衬衫是这家店里最大的。那个黑衬衫比蓝衬衫小。