Extra virgin olive oil, also you have to be careful, there's a huge market of extra virgin olive oil mixed with cheaper oils sold as actual extra virgin olive oil. A way you can determine this, is by putting it in the fridge, although even this isn't 100% conclusive.
Extra virgin olive oil is comprised of mainly monounsaturated fat that gets more solid when cold. If you put a real extra virgin olive oil in the fridge, it ought to become thick and cloudy as it cools completely.
However, if the oil you put in the fridge fails to thicken at all, then you know it's probably mixed with cheaper oils.
Bertolli brands are not to be trusted, they already have been derided for their involvement in selling extra virgin olive oil mixed with canola oil.