A transfer agent is responsible for maintaining accurate records of shareholder purchases, redemptions, and account balances. They also handle the issuance and cancellation of shares and ensure shareholders receive appropriate distributions.

D is correct because maintaining shareholder records is a core duty of a transfer agent.

A is incorrect because underwriting is the responsibility of a broker-dealer.

B is incorrect because distributing the prospectus is handled by the fund’s distributor.

C is incorrect because custody of securities is the role of a custodian, not the transfer agent.