I didn't know what this meant in a choose-the-word question and I still don't now I've seen the English. Does it mean 'the number 2', in which case dhà would be correct, or does it mean '2 (cats or something) in which case dà would be correct.
Having 2 choices when both could be right is a pointless question.
I thought it would have to be dhà because no noun follows it.
From the Scottish Gaelic section of https://en.wiktionary.org/wiki/dà,
dhà is used when free-standing (counting, telling a row of numerals etc).
Tha dà chàr aige. ― He has two cars.
Tha a dhà aice cuideachd. ― She has two as well.
Fòn a h-aon, a h-aon, a dhà! ― Phone one-one-two!
If it was referring to the number two, like you are playing bingo. But I was assuming you had been asked how many Easter eggs you have found:
Do you have three yet? No I don't have two yet.
In this case I would have thought, but I don't know, that dà was actually short for dà ubh. But I may be wrong, both in terms of grammatical analysis and in terms or correct Gaelic. I would like to hear from anyone who knows either answer.