Learn English – A question about ‘must have been someone’

grammarpast-continuouspast-perfect

I am recently struggling with the grammar MUST HAVE BEEN.

My question is can i say

"It must have been someone stealing/ stole / who stole my wallet "

I think who stole is right, but might also be stealing, because one sentence can not have two verbs ? so the second one has to be turned into ING form.

can anyone tell me which on is correct and the grammar behind this ?

Much appreciated !

Best Answer

Sentences can have multiple verbs in them, actually (remember, the sentence is the everything from the first word to a period).
"Stealing" and "who stole" my wallet both work, although they have different meanings.
If you're talking about someone who stole your wallet, you'd refer to them with "It must have been someone who stole my wallet".
If you're talking about the event in which your wallet was stolen, it would be "It must have been someone stealing my wallet".
If you're trying to say that the reason your wallet is missing is that it was stolen, you might consider "Someone must have stolen my wallet" or "It must have been that someone stole my wallet".
Incidentally, "have been" followed by the gerund form ("ing" for most verbs) puts the verb in the "Perfect Indicative" form.