The rest of the options are not given but there can only be one correct answer to this question and that's the answer above.
Brokerages earn a return when they trade financial instruments for investors as they take a commission from this. When an investor has not traded for a while, brokerages don't get to make earnings and will be holding the account with minimal rewards.
To compensate for this, they charge an inactivity fee that will ensure that they get some form of earnings for managing the account and not receiving commission.
