Open-end mutual funds do not trade on secondary markets. Instead, shares are continuously issued or redeemed by the fund at the net asset value (NAV), calculated at the market close.

D is correct because investors purchase and redeem shares directly through the fund or authorized brokers.

A is incorrect because mutual funds do not have a predetermined dissolution date.

B is incorrect because mutual fund shares are priced at the NAV calculated once daily after the market closes.

C is incorrect because secondary market trading applies to closed-end funds and ETFs, not open-end mutual funds.