2. Which

1. Which (pronoun, interrogative): Dore (do-re)
2. Which (pronoun/adjective): Dono (do-no)
3. Which (adjective, polite): Dochira (do-chi-ra)

Examples:

1.a. Dore desu ka - Which one is it?
b. Anata no tori wa dore desu ka - Which one is your bird?
c. Dore ga anata no tori desu ka - (emphasises 'which one'. Well, there are many birds here...) Which one (of all the birds) is your bird? (If a sentence starts with a question word, it should have GA as a topic/subject marker instead of WA) (taken from yesjapan.com)

2. Dono gakusei o erabimasu ka - Which student would you select?

3. Dochira ga anata no desu ka - Which one is yours?

moonlit dream's note: Dore and dochira are essentially the same thing; but dochira is only used as "which" between two objects, while "dore" is for 3 or more objects. :D

Help from internet (Yahoo answers, Ririshii):

"Basically the d- words are question words. If "kore" is "this one", "dore" means "which one". Kono - this, dono - which. Koko -here, doko - where. Kochira - here, this person , dochira - where, which person

Notce that every one of these words also have an s- equivalent pointing towards the hearer (near the hearer): kore - SORE (that one) / kono - sono (that) / koko - soko (there) - kochira - sochira (that place, there, that person)

And also an a- equivalent, which points towards a place that is not near the speaker or the herarer:

Are (that one over there), ano (that... over there), asoko (over there), achira (over there, that person over there)"

End