It sounds correct to me to say.
She is actually a man. (Regardless how weird the sentence is)
But in this situation as we take plural subject.
they are actually surprises.
It sounds a bit odd like I am using the adverb to modify the noun (surprises), although it's intended for the verb to be.
Can we say
they are actually a surprise.
Is there any rule that explains what should we use after plural subject + to be, singular noun or it has to be plural? or we can use both, and is this sentence they are actually surprises correct?
And what is the official term of this Noun/prounoun + to be + noun Thanks in advance.