A trusted system is one that meets its intended security requirements. It involves sufficiency and effectiveness, not necessarily efficiency, in enforcing a security policy. Put succinctly, trusted systems have (1) policy, (2) mechanism, and (3) assurance. Source: HARE, Chris, Security Architecture and Models, Area 6 CISSP Open Study Guide, January 2002.

Computer worms are also known as Network Mobile Code, or a virus-like bit of code that can replicate itself over a network, infecting adjacent computers.
A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers. Often, it uses a computer network to spread itself, relying on security failures on the target computer to access it. Unlike a computer virus, it does not need to attach itself to an existing program. Worms almost always cause at least some harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.
A notable example is the SQL Slammer computer worm that spread globally in ten minutes on January 25, 2003. I myself came to work that day as a software tester and found all my SQL servers infected and actively trying to infect other computers on the test network.
A patch had been released a year prior by Microsoft and if systems were not patched and exposed to a 376 byte UDP packet from an infected host then system would become compromised.
Ordinarily, infected computers are not to be trusted and must be rebuilt from scratch but the vulnerability could be mitigated by replacing a single vulnerable dll called sqlsort.dll.
Replacing that with the patched version completely disabled the worm which really illustrates to us the importance of actively patching our systems against such network mobile code.
The following answers are incorrect:
-Rootkit: Sorry, this isn't correct because a rootkit isn't ordinarily classified as network mobile code like a worm is. This isn't to say that a rootkit couldn't be included in a worm, just that a rootkit isn't usually classified like a worm. A rootkit is a stealthy type of software, typically malicious, designed to hide the existence of certain processes or programs from normal methods of detection and enable continued privileged access to a computer. The term rootkit is a concatenation of "root" (the traditional name of the privileged account on Unix operating systems) and the word "kit" (which refers to the software components that implement the tool). The term "rootkit" has negative connotations through its association with malware.
-Adware: Incorrect answer. Sorry but adware isn't usually classified as a worm. Adware, or advertising-supported software, is any software package which automatically renders advertisements in order to generate revenue for its author. The advertisements may be in the user interface of the software or on a screen presented to the user during the installation process. The functions may be designed to analyze which Internet sites the user visits and to present advertising pertinent to the types of goods or services featured there. The term is sometimes used to refer to software that displays unwanted advertisements.
-Logic Bomb: Logic bombs like adware or rootkits could be spread by worms if they exploit the right service and gain root or admin access on a computer.
The following reference(s) was used to create this question:
The CCCure CompTIA Holistic Security+ Tutorial and CBT and http://en.wikipedia.org/wiki/Rootkit and http://en.wikipedia.org/wiki/Computer_worm and http://en.wikipedia.org/wiki/Adware

Section: Security Operation Adimnistration
Explanation/Reference:
The best way to properly verify an application or system during a stress test would be to expose it to "live" data that has been sanitized to avoid exposing any sensitive information or Personally Identifiable Data (PII) while in a testing environment. Fabricated test data may not be as varied, complex or computationally demanding as
"live" data. A production environment should never be used to test a product, as a production environment is one where the application or system is being put to commercial or operational use. It is a best practice to perform testing in a non-production environment.
Stress testing is carried out to ensure a system can cope with production workloads, but as it may be tested to destruction, a test environment should always be used to avoid damaging the production environment. Hence, testing should never take place in a production environment. If only test data is used, there is no certainty that the system was adequately stress tested.
Incorrect answers:
Test environment using test data. This is incorrect because live data is typically more useful during stress testing Production environment using test data. This is incorrect because the production environment should not be used for testing.
Production environment using live workloads. This is incorrect because the production environment should not be used for testing.
Source: Information Systems Audit and Control Association, Certified Information Systems Auditor 2002 review manual, chapter 6: Business Application System Development, Acquisition, Implementation and Maintenance (page 299).
And:
KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 251.
And:

Remotre Procedure Call (RPC) is the only of the above choices to operate at the session layer (layer 5).
All of the other answers were wrong.
LPD operates at layer 7 SPX operates at layer 4 IGMP operates at layer 3.
Reference:
WALLHOFF, John, CBK#2 Telecommunications and Network Security (CISSP Study Guide), April 2002 (page 1).