Capitulum xxxii, pensum a -- why subjunctive?

In the sentence “Ergo dic mihi cur heri ovis e grege aberraverit ac paene a lupo capta sit” why are the verbs in the subjunctive? I know the sentence means “Tell me why last night a sheep strayed from the flock and was almost captured by a wolf?”

This is just a statement of fact, so I don’t know why those two verbs are in the subjunctive.

Subjunctive in indirect question. Cf. Catullus’ odi et amo. quare id faciam fortasse requiris.