how can we tell what's the verb and what's the subject? the subject will obviously be the thing of interest in the sentence, so it's the watering can.
How do we find the verb? the verb is an action or something that the subject is doing; the watering cans "are." this kind of verb is called a passive verb, and it matches the subject in this sentence because the subject is plural. (this is a bit weird to explain, sorry for any confusion.)
