The Belta fund is a closed-end fund selling at a premium. Closed-end funds are a type of investment company whose shares are traded on the open market, like stocks or ETFs. The price of these shares fluctuates based on market demand and can deviate from the fund's Net Asset Value (NAV). When the trading price of a closed-end fund is higher than its NAV, it is said to be trading at a 'premium'. In this case, the Belta fund's trading price ($1850) is higher than its NAV ($1600), indicating that it is indeed a closed-end fund selling at a premium.

Choice B is incorrect. A closed-end fund selling at a discount would mean that the trading price of the fund is less than its Net Asset Value (NAV). In this case, however, the trading price ($1850) is higher than the NAV ($1600), indicating that it's not selling at a discount.

Choice C is incorrect. Open-end funds do not trade on exchanges and their prices are not determined by market forces of supply and demand but are instead directly related to their NAV which is calculated at the end of each trading day. Therefore, an open-end fund cannot sell at a premium or discount.

Choice D is incorrect. Similar to Choice C, open-end funds do not trade on exchanges and their prices are directly related to their NAV calculated daily. Hence, they cannot sell at a premium or discount.