Two analogies on manipulating items in a kitchen is given in the form "A : B. C : ?". The phrase "A : B" relates item A to its appropriate manipulation B. Your task is to replace the question mark (?) with the appropriate manipulation of item C, following the "A : B" relation. Your answer should be a verb which shows a way to manipulate the given object.

candy : unwrap. suitcase : ?
open

safe : unlock. suitcase : ?
open

walnut : shell. backpack : ?

unzip