Final answer:
The answer is A) One. Only one custodian is typically allowed per minor's custodial account to ensure that the funds are responsibly managed for the minor's benefit.
Step-by-step explanation:
The correct answer to the question 'Only ______ custodian is allowed per minor's account' is A) One. In the context of custodial accounts such as the Uniform Transfers to Minors Act (UTMA) or Uniform Gifts to Minors Act (UGMA) accounts, typically only one adult custodian is appointed to manage the account on behalf of the minor. This arrangement ensures that the funds are managed responsibly and used for the benefit of the minor until they reach the age of majority or the age specified for the termination of the custodianship.