is 'bong bong' a plural word? if not should there be a 'cac' or 'nhung"
Generally speaking when you say you're selling an item, that item is interpreted as being plural without need to specify through added counting words. "Tôi bán bông/hoa" = I sell flowers.
Based on Duolingo, it's plural but also not.
It's not plural, it's indefinite (which we express as plural in English, and without a classifier in Vietnamese).
5/3/2023 - no "bong bay" this time, to trip us up????
According to Wiktionary this means ‘sac; bladder’...