'which of the names' vs. 'what of the names'

[Kalida]

English Grammar Tests, Elementary Level

ESL/EFL Test #100 "Interrogative pronouns", question 5

......... of the names did you choose for the puppy?

(a) What
(b) Which
(c) Who
(d) Whom

English Grammar Tests, Elementary Level

ESL/EFL Test #100 "Interrogative pronouns", answer 5

Which of the names did you choose for the puppy?

Correct answer: (b) Which

Your answer was: incorrect
What of the names did you choose for the puppy?
_________________________

hi!

Why which of the names and no what of the names?

Kalida

[Conchita]

If you want to use 'what' you have to say:

What name did you choose for the puppy?