In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.

Question: When did the Northern Mariana Islands become a territory of the United States? Passage:The One Hundred Eleventh United States Congress was a meeting of the legislative branch of the United States federal government from January 3, 2009, until January 3, 2011. It began during the last two weeks of the George W. Bush administration, with the remainder spanning the first two years of Barack Obama's presidency. It was composed of the Senate and the House of Representatives. The apportionment of seats in the House was based on the 2000 U.S. Census. In the November 4, 2008 elections, the Democratic Party increased its majorities in both chambers, giving President Obama a Democratic majority in the legislature for the first two years of his presidency. A new delegate seat was created for the Northern Mariana Islands. The 111th Congress had the most experienced members in history: at the start of the 111th Congress, the average member of the House had served 10.3 years, while the average Senator had served 13.4 years.
Links: a. 2008 United States elections b. Northern Mariana Islands c. Presidency of Barack Obama d. United States House of Representatives
b