To determine the requirements for administrator authentication, the user must understand the concept of administrator accounts and their privileges.

Admin accounts have higher privileges than normal user accounts and can perform tasks that can affect the entire system. Therefore, they require greater security measures to prevent unauthorized access and misuse of their privileges.

Option A is incorrect because the authentication requirements for administrators should be greater than those of normal users.

Option B is incorrect because all administrators cannot be considered trustworthy. They may intentionally or unintentionally cause harm or damage to the system.

Option C is incorrect because no authentication for administrators would pose a significant security risk and make the system vulnerable to attacks.

Option D is correct because administrators require greater authentication requirements to ensure that only authorized personnel can access their accounts and perform tasks that can affect the system.

Therefore, the answer is: D. Greater than those of normal users.