Final answer:
ETFs can be registered as both unit investment trusts (UITs) and open-end funds, but the most common form of registration is as an open-end fund.
Step-by-step explanation:
ETFs, or Exchange-Traded Funds, can be registered as both unit investment trusts (UITs) and open-end funds. However, the most common form of ETF registration is as an open-end fund.
An open-end fund is a type of investment fund that allows investors to buy and sell shares at the net asset value (NAV) of the fund. The number of shares in an open-end fund is not fixed and can change based on investor demand.
On the other hand, a unit investment trust (UIT) has a fixed number of shares, which are bought and sold through a different mechanism. UITs typically have a fixed portfolio of securities with a predefined investment objective.