The fact that the verb "announce" is in the past tense means that you definitely cannot use future or present after it. It's a rule of "coordination of tenses", so to speak. You need to have either past there, or use something like a gerund or an infinitive.

Option D is eliminated because the arrangement of the words in the sentence are not appropriate. Plus, "announced to" is not idiomatic, you only "announce that something".

Thanks DanaJ, it really helped to trace the mistake.