Open-end funds do not sell shares at a premium or a discount to net asset values depending on the demand for the shares. Instead, new shares in open-end funds are issued at the fund's net asset value at the time of investment. This is a key characteristic of open-end funds and differentiates them from closed-end funds. Closed-end funds, on the other hand, typically issue all the shares they will issue at the outset, with such shares usually being tradable between investors thereafter. These shares are typically traded lower than their net asset value, which can be attributed to management fees. Therefore, the statement in choice B is incorrect and does not accurately describe a characteristic of open-end mutual funds.\n\nChoice A is incorrect. This statement accurately describes a characteristic of open-ended mutual funds. Open-end funds do indeed accept new investment money and issue additional shares to existing or new investors, which results in the number of outstanding shares changing after every new investment.\n\nChoice C is incorrect. This statement also correctly describes a characteristic of open-ended mutual funds. The structure of these funds does make it easy for them to grow in size, but it also creates pressure on the portfolio manager to manage cash inflows and outflows effectively.\n\nChoice D is incorrect. As explained above, both choices A and C accurately describe characteristics of open-ended mutual funds, so this choice cannot be correct.