Final answer:
The taxable year ends on December 31 because more LLC members use a calendar year than any other year, according to the majority interest rule.
Step-by-step explanation:
The correct answer is c. The taxable year ends on December 31 because more LLC members use a calendar year than any other year.
This is determined by the majority interest rule, which states that the taxable year end of an LLC is determined by the taxable year end of the majority of its partners. In this case, 42% of the LLC members own interests of 4% or less and use the calendar year (December 31), making it the most common taxable year end.
SwanCo and QuinnCo, who both have a June 30 tax year end, do not fulfill the requirement to determine the taxable year end for the entire LLC.