Answer:
(b) selecting and training new hires at the firm
Explanation:
Circular 230 requirement states that a practitioner must exercise due diligence in respect of those matters which relate to preparing, approving and filing tax returns or any other paper to Internal Revenue Services(IRS).
Due Diligence basically means to ensure that actions and information supplied are correct and not false.
So basically it extends to oral or written representations made to IRS or to a client in respect of matter which are administered by IRS.
Selecting and training new hires at the firm does not relate to IRS.