Answer this question mentioning about the apps which have specifically caught your eye and it is not necessary that they are to be popular. What is special about it, what are the features, colors, the design aspect you like in it and justify with the logical reasoning as to how all of it works for the best. What will be your opinion on it and mentioning the synchronicities of all those elements that makes it the best visually.

This answer should tell the employer as to what kind of feature and attributes are your personal style and how as a designer you will be incorporating it into the work while maintaining the individuality of the brand.