Which other organisations have you applied to work for?

The employer does not want a candidate whom every other company has rejected. They feel their organisation is special and offering you the job represents a big investment. You want to convey the impression that you feel this particular vacancy is exactly the right one for you, and you have been saving yourself for it. I recommend that you say you are being choosy about the companies you approach. In other words, imply that you have not found such an interesting vacancy as this before, and say why.