it was not immediately obvious that water was to be fundamental to the development of life

题目

it was not immediately obvious that water was to be fundamental to the development of life
为什么water was 后面要加to

答案

因为water=somebody.was=be动词.
be to do 表示将要做某事可以用,且表示1）按计划或安排要做的事 2）表示指令,相当于should,ought to,must,have to,This meicine is to be taken three times a day.3) 表示 想,打算,相当于intend to ,want to If you are to listen to the consert,you'd better hurry up.