It depends on which exercise brought us here. There are several exercices on the same grammatical point and they all leads here. So, if someone gets the exercise of writing down in french what he/she hears, then both sigular and plural forms are possible since they sound exactly the same.
That is a good question. The answer is that the French does not have a verbal form equivalent to the English continuous tense (be verb-ing). But you have an expression which means exactly the same idea of an action in progress: "être en train de".
So, "she is speaking" = "elle est en train de parler".