The plan __ to be a good one.A.proved B.was proved 哪个对?

The plan __ to be a good one.A.proved B.was proved 哪个对?
1) prove是vt,可以带复合宾语prove sth to be+n/adj
则The plan proved to be a dood one=The plan was proved to be a dood one是对的
2)prove是vi,可以带to be +n/adj
则The plan proved to be a dood one也是对的
但是被动语态by+主动语态主语宾格不是常常省略了么？难道只有说
The plan was proved to be a dood one by them才对么？