Question word: welch-

Welcher Salat ist am besten? – Der Salat „Fantasia“ schmeckt sehr gut.

Welchen Salat möchten Sie? – Den Salat „Fantasia“, bitte.

The question word welch-, is used to ask about a particular person or thing or to select one thing from a larger number of items.

The question word welch- appears before a noun and takes the same ending as that which a definite article would take. 

  Nominative Accusative
Masculine (der) welcher welchen
Feminine (die) welche welche
Neuter  (das) welches welches
Plural (die) welche welche