C.to be
to be one of the most useful tools in use today 是to be 不定式短语在句中作宾补
being ...这类的分词短语,不可以作think 的补足语,故排除A
如果把后面的复合宾语改为宾语从句,即为:
We think (that) the electronic computer[ is] one of the most useful tools in use today
能接to be 不定式短语在句中作宾补的动词有:
think,consider,suppose,declare 等
再如:
I suppose him to be an honest boy.
我认为他是个诚实的男孩子