I used to use the particule が in the sentence, since I was taught that the potential form of a verb (可能形) did not direct objects :
日本語が話せます
but I recently bumped into this sentence in the example section of the Tangorin website
イタリア語を話せますか?
Is it actually possible to use both ? Is there a difference ?
I'm not native Japanese speaker.
basically, を is for object.
like 日本語が話せます, using ーが and 可能形, it's mean, there are some selections, and I can (verb) the selection.
both them are okay, but ーを可能形 is more basic thing, ーが and 可能形 is more emphasis on the object of verb.