这是一个固定搭配,be to do意思是“表示应该发生什么”,翻译下来就是,狗儿们应该是很好养的.
而且be to do 还有其他的意思
1.表示命令和规则 all prisoners are to be in bed by 10o'clock.
2.表示将来的安排 we are to be married in June.
3.表示不能或不会发生什么 we looked and looked,but the ring was nowehere to be found.
4.表示不得不发生或者已发生什么 This discovery was to have a major effect on the treatment of heart disease.
5.用于虚拟语气表示与事实相反的情况 if I were to do that,what woulld you say?