何

何 means "what". It has two readings, and which one to use depends on what follows:

• なん before です, before の, before counters (何時, 何人, 何回) and before words starting with t, d or n sounds: これは何ですか, 何時ですか.
• なに before を, が, も and most other particles: 何を食べますか, 何がほしいですか.

Get it wrong and you'll still be understood, but it's one of the first things listeners notice.

何 doesn't pick from a set: for "which one", use どれ. And for "what kind of", どんな is more natural than 何の.