Members of the government acknowledge many of their predictions__over-optimistic.答to have been为何

题目

Members of the government acknowledge many of their predictions__over-optimistic.答to have been为何

答案

首先,承认某物怎么样可以用这个句型 acknowledge sth to be + adj.
He acknowledged it to be true/that it was true.他供认那是事实.
第二,政府成员承认许多他们（之前）的预测过于乐观了.
因为是对之前的预测做评价,所以用完成时态.
综合以上,答案为to have been.
Thanks to newdict!