No. But this specific syntactic form does require the past participle. Let me explain. You wrote 'It can be done' this is called a passive sentence. We use this form to denote that the subject undergoes an action. What the subject is

Actually, there's another aspect to this. This might be over-complicating things, so if it just confuses you then ignore it. In the passive sentence "The vase was broken by John", it's important that the vase was broken by

I'd say sentence 11 is by far the most difficult of these. Nevertheless, the only thing you need to do is find the subject, verb and object in the active sentence, and then use the object as the subject in the passive sentence. Who made these

how could we make sure whether we are looking at a passive sentence or a sentence with a "be" verb followed by an adjective in cases like this I think you have already solved your own problem. The other words in the sentence, like by Joe