The UN envoy came to Bangladesh on ___ visit.

• When a number joins a noun with a hyphen to describe another noun, the noun stays singular: a three-day visit, a ten-year-old boy. It never takes -s. অন্য অপশনগুলো কেন নয়: - a three-days, three-days, the three-days — either the plural -s or the missing article makes them wrong