How do you say this in English (US)? which one goes in the blank?

If possible, i'd like you tell me why. (you don't have to when you're busy. Thank you. )

Could humans live on indefinitely were it not for ( ) age-related diseases?

①some ②little ③no ④few

See a translation

1.

"X were it not for Y" is like "If not Y, then X". X would be true or possible or desirable, but Y prevents it.

It would be quiet outside were it not for the cats fighting in the backyard. (= "it is quiet outside" is not possible because "the cats fighting in the backyard" is happening)
She would be beautiful were it not for the big scar on her forehead. (= "she is beautiful' is not true because "the big scar on her forehead" prevents it)

The word in the blank can't be "no". "No age-related diseases" do not prevent "humans live on indefinitely".
It can't be "little". "Little" can only modify uncountable nouns.
It isn't "few". "Few" emphasizes the small number of something. It sounds strange to use "were it not for" to emphasize the problem of "age-related diseases", then immediately use "few" to minimize it.
That leaves "some".