You are creating a new security policy for an application domain. You write the following lines of code.  PolicyLevel policy = PolicyLevel.CreateAppDomainLevel（）；  PolicyStatement noTrustStatement =    new PolicyStatement（  policy.GetNamedPermissionSet（"Nothing"））； PolicyStatement fullTrustStatement =    new PolicyStatement（  policy.GetNamedPermissionSet（"FullTrust"））；  You need to arrange code groups for the policy so that loaded assemblies default to the Nothing permission set. If the assembly originates from a trusted zone， the security policy must grant the assembly the FullTrust permission set.  Which code segment should you use？（）

• A、A
• B、B
• C、C
• D、D