You will be given a definition of a task first, then some input of the task.
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: How long did the Battle of Luang Namtha take place? Passage:Following the defeat of Royal Lao Army in the Battle of Luang Namtha in early May 1962 by People's Army of Vietnam and Pathet Lao forces, it appeared that a communist invasion of northern Thailand was imminent and on 15 May the Kennedy Administration ordered US combat forces into Thailand to deter any attack. On 18 May VMA-332 equipped with 20 A-4 Skyhawks deployed to Udorn from Naval Air Station Cubi Point in the Philippines and HMM-261 helicopters flew into the base. On 19 May detachments of Marine Air Control Squadrons 1 and 4 and Marine Air Base Squadron 12 were also flown into the base. On 19 May the command group of the 3rd Marine expeditionary brigade and the Battalion Landing Team 3rd Battalion, 9th Marines began flying in from Bangkok and then moved north to the town of Nong Khai. The Marines conducted field training exercises with the Royal Thai Army and civic action with Thai civilians while Naval Mobile Construction Battalion Ten which arrived in late May established a base camp and repaired public buildings. In late June HMM-162 replaced HMM-261.
Links: a. VMFA(AW)-332 b. Philippines c. Battle of Luang Namtha d. Douglas A-4 Skyhawk
Output:
c