The correct answer is D, Discretionary. A discretionary account allows a registered representative (RR) to make investment decisions and execute trades on behalf of the client without obtaining prior approval for each transaction. This directly matches the scenario described in the question.

Step-by-step, discretionary authority must be granted in writing by the customer and approved by the firm’s principal before it can be exercised. Once approved, the RR can determine what securities to buy or sell and when to execute trades, although the account must still be managed in accordance with the customer’s investment objectives and suitability requirements.

Choice A, margin, refers to borrowing money to purchase securities and does not grant trading authority to the RR. Choice B, options, is a type of account used for trading options contracts and also does not provide discretionary authority. Choice C, custodial accounts are established for minors and managed by an adult custodian, not applicable in this situation.

Thus, when an investor wants the RR to control investment decisions and timing of trades, a discretionary account is required, making Answer D correct.