The original disk of a computer involved in a criminal investigation
should not be used for any experimental purposes since data
may be modified or destroyed. Any operations should be conducted
on a copy of the system disk. However, the other answers are
the preferred methods of gaining access to a password-protected system.
Interestingly, in answer b, there is legal precedent to order a suspect to provide the password of a computer that is in the custody of law enforcement.

organizational policies and procedures, pre-employment background checks, strict hiring practices, employment agreements, friendly and unfriendly employee termination procedures, vacation scheduling, labeling of sensitive materials, increased supervision, security awareness training, behavior awareness, and sign-up procedures to obtain access to information systems and networks. Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 34

Explanation/Reference:
Explanation:
A few years ago the best choice for this question would have been seeing how far their skills can take them. Today this has changed greatly, most crimes committed are financially motivated. Profit is the most widespread motive behind all cybercrimes and, indeed, most crimes- everyone wants to make money.
Hacking for money or for free services includes a smorgasbord of crimes such as embezzlement, corporate espionage and being a "hacker for hire". Scams are easier to undertake but the likelihood of success is much lower. Money-seekers come from any lifestyle but those with persuasive skills make better con artists in the same way as those who are exceptionally tech-savvy make better "hacks for hire".
"White hats" are the security specialists (as opposed to Black Hats) interested in helping the community in securing their networks.
They will test systems and network with the owner authorization. A Black Hat is someone who uses his skills for offensive purpose. They do not seek authorization before they attempt to comprise the security mechanisms in place. "Grey Hats" are people who sometimes work as a White hat and other times they will work as a "Black Hat", they have not made up their mind yet as to which side they prefer to be. The following are incorrect answers: All the other choices could be possible reasons but the best one today is really for financial gains.
References:
http://library.thinkquest.org/04oct/00460/crimeMotives.html
and http://www.informit.com/articles/article.aspx?p=1160835
http://www.aic.gov.au/documents/1/B/A/%7B1BA0F612-613A-494D-B6C5-06938FE8BB53%
7Dhtcb006.pdf