Qian Ge-chuan, a famous Chinese scholar of English, holds in his Chinese book << A Sequence to English Difficulties Explanations >>(p.83) in 1981 that "The plan was proved a failure." is wrong. The word "was" should be omitted. Because here to prove means to turn, and is an intransitive verb. In the same way ,in the following two sentences "Great advantages are accrued from this measure." and "What will be ensued on this?" ,the words "are " and "be" should be omitted,too.