I think you should make your question more clear. I have no idea on '가' to make a noun plural, we just add '들' to persons or objects(nouns). However, the plural marker '들' in Korean is not so obligatory as in English. I think this is because that English by itself focuses on listeners, but the Korean language focuses on speakers. In my opinion, this is one of big differences between both languages. for example, 사람(a person) - 사람+들 (persons or people) 친구(a friend) - 친구+들 (friends) 사과(an apple) - 사과+들(apples), but as the plural form of '사과' is also acceptable. (the plural marker is very often omitted so don't be panic. :) ) When we don't need to make things clear, we don't put the plural marker '들', so that "apples' can be '사과' or '사과들' in our language,but mostly '사과' is more natural even if it is translated into 'apples' in English.