do you like Mr Green`s lesson?

do you like Mr Green`s lesson?
【1】do you like Mr Green`s lesson?
——yes,mo one teaches（better）.
【为什么用better而不是best?】
【2】which is （the best）season in Beijing?
——i think it is winter.
【为什么用the best不用best?】
【3】can you afford the computer?
——no,the price of it is too（high）.
【为什么用high而不是expensive?】