whichever

An interrogative word or question word is a function word used to ask a question, such as what, which, when, where, who, whom, whose, why, whether and how. They are sometimes called wh-words, because in English most of them start with wh-. Most may be used in both direct and in indirect questions. In English and various other languages the same forms are also used as relative pronouns in certain relative clauses and certain adverb clauses. It can also be used as a modal, since question words are more likely to appear in modal sentences, like Read more on Wikipedia