Q: I was admitted to the U.S. under a K visa. However, I did not marry my fiancé who petitioned for me. I ended up marrying another U.S. citizen instead. May I adjust my status? 
A: No. You have to leave the U.S. and apply for an immigrant visa at a U.S. Consulate. 

Q: I am a legal permanent resident. I want to petition for a family visa for my husband, but I realize that he will have to wait over four years until he is eligible to apply for adjustment. Since I am planning on getting my U.S. citizenship next year, should I just wait until then to help my husband apply for adjustment? 
A: You can certainly do so since this may be faster. You may also file the immigration petition now as a permanent resident. Once you become a citizen, you may request your case be upgraded. 

Q: What is a derivative beneficiary? 
A: Typically, a derivative beneficiary is an immediate family member of the principal beneficiary of an approved immigration petition. A derivative beneficiary may apply for an immigrant visa or adjust his/her status to permanent resident if the principal beneficiary is eligible to apply or adjust. For example, if a man is eligible to adjust his status based on an approved immigration petition filed by his U.S. citizen sister, this man's wife and minor children may also adjust their status in the U.S. The wife and the minor children are derivative beneficiaries.