The correct answer should be ID based access control. Rule based isn't necessarily identity based.

Since the circuit level proxy does not anayze the application content of the packet in making its decisions, it has lower overhead than an application level proxy.
"More difficult to maintain" is incorrect. Circuit level proxies are typicall easier to configure and simpler to maintain that an application level proxy.
"More secure" is incorrect. A circuit level proxy is not necessarily more secure than an application layer proxy.
"Slower" is incorrect. Because it is lower in overhead, a circuit level proxy is typically faster than an application level proxy.
References: CBK,pp. 466 - 467 AIO3, pp.488 - 490

The criteria are divided into four divisions: D, C, B, and A ordered in a hierarchical manner with the highest division (A) being reserved for systems providing the most comprehensive security.
Each division represents a major improvement in the overall confidence one can place in the system for the protection of sensitive information.
Within divisions C and B there are a number of subdivisions known as classes. The classes are also ordered in a hierarchical manner with systems representative of division C and lower classes of division B being characterized by the set of computer security mechanisms that they possess.
Assurance of correct and complete design and implementation for these systems is gained mostly through testing of the security- relevant portions of the system. The security-relevant portions of a system are referred to throughout this document as the Trusted Computing Base (TCB).
Systems representative of higher classes in division B and division A derive their security attributes more from their design and implementation structure. Increased assurance that the required features are operative, correct, and tamperproof under all circumstances is gained through progressively more rigorous analysis during the design process.
TCSEC provides a classification system that is divided into hierarchical divisions of assurance levels:
Division D - minimal security Division C - discretionary protection Division B - mandatory protection Division A - verified protection Reference: page 358 AIO V.5 Shon Harris
also
Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, page 197.
Also:
THE source for all TCSEC "level" questions: http://csrc.nist.gov/publications/secpubs/rainbow/std001.txt

These laws reflected different views concerning wiretapping as
technology progresseD. The Federal Intelligence Surveillance Act
(FISA) of 1978 limited wiretapping for national security purposes as a
result of the record of the Nixon Administration in using illegal wiretaps.
The Electronic Communications Privacy Act (ECPA) of 1986
prohibited eavesdropping or the interception of message contents
without distinguishing between private or public systems. The Communications
Assistance for Law Enforcement Act (CALEA) of 1994
required all communications carriers to make wiretaps possible in
ways approved by the FBI.

A blind signature algorithm for the message M uses a blinding
factor, f; a modulus m; the private key, s, of the signer and the public key, q, of the signer. The sender, who generates f and knows q, presents the message to the signer in the form:
Mf q (mod m)
Thus, the message is not in a form readable by the signer since the
signer does not know f. The signer signs Mf q (mod m) with his/her
private key, returning
(Mf q)s (mod m)
This factor can be reduced to fMs (mod m) since s and q are
inverses of each other. The sender then divides fMs (mod m) by the
blinding factor, f, to obtain
Ms (mod m)
Ms (mod m) is, therefore, the message, M, signed with the private
key, s, of the signer.
Answer Zero knowledge proof refers to a zero knowledge proof. In general, a zero knowledge proof involves a person, A, trying to prove that he/she knows something, S, to another person, B, without revealing S or
anything about S. Answers Masked signature and Encrypted signature are distracters.