Name the countries where at least part of the country has a tropical monsoon climate according to the Köppen climate classification
Not including overseas territories or regions
According to these maps: https://upload.wikimedia.org/wikipedia/commons/3/32/Köppen-Geiger_Climate_Classification_Map_%281980–2016%29_no_borders.png and https://upload.wikimedia.org/wikipedia/commons/e/e8/Koppen-Geiger_Map_World_present.svg
If you look at a detailed Köppen climate map of the Caribbean (you can find it on Wikimedia Commons), neither of those countries have that climate. Antigua is too dry, and is classified as tropical savanna, whereas Dominica and St Lucia are tropical rainforest.