"Est-ce nécessaire ?"
Translation:Is it necessary?
The audio pronounces the « -aire » part like '-er' in American English. That accent is quite weird and doesn't sound right to me. I've reported it.
You forgot « est » « est-ce qu'il est nécessaire » ou « est-ce que c'est nécessaire »
I've never seen "est-ce" before. What is the difference between that and "est-il'?
I still don't feel comfortable enough yet to explain where you'd use one or the other, but if you'd use "c'est," then inverting it gives you "est-ce," and if you'd use "il est" then you'd use "est-il." You've surely seen it before, at least in questions beginning with "est-ce que."
The difference is explained very well here: