补全对话：根据对话内容从方框中选出能填入空白处的最佳选项。

A: Do you like living in the city or the countryside?

B: __1_____

A: But I think the countryside is much better than the city for living.

B: ___2_____

A: Because there is terrible traffic and too much noise in the city.

B: ___3____ I think the city is a wonderful place to live in, because we can go to parties, concerts and operas every day if we like.__4____

A: Maybe you are right. ____5___

____年我国科学家在世界上第一次用人工方法合成了具有生命活力的蛋白质__________， 这对蛋白质和生命的研究做出了贡献。