Trailer fees are ongoing fees that are paid by mutual fund managers to mutual fund dealers for providing ongoing services to their clients who hold units of their funds. Trailer fees are calculated as a percentage of the value of assets under management (AUM) of the clients who hold units of the fund. Trailer fees are paid out of the management fee that is charged by the mutual fund manager to cover the costs of operating and administering the fund. Therefore, option C is correct regarding mutual fund fees. The other options are incorrect. Option A is false because redemptions are not made from units held by investors to pay trailer fees; rather, trailer fees are paid out of the management fee that is deducted from the net asset value (NAV) of the fund. Option B is false because trailer fees are not only paid to mutual fund dealers when a purchase is made; rather, trailer fees are paid on an ongoing basis as long as the clients hold units of the fund. Option D is false because trading commissions are not paid from the management fee; rather, trading commissions are paid from the trading expense ratio (TER) that reflects the costs of buying and selling securities within the fund. References: [Mutual Fund Fees Explained | Wealthsimple], [Mutual Fund Fees | GetSmarterAboutMoney.ca], [Understanding Mutual Fund Fees | Investopedia]