Given the task definition and input, reply with output. 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: Did the Battle of Pakchon take place in North Korea or in South Korea? Passage:The Battle of Pakchon (5 November 1950), also known as the Battle of Bochuan (), took place ten days after the start of the Chinese First Phase Offensive, following the entry of the Chinese People's Volunteer Army (PVA) into the Korean War. The offensive reversed the United Nations Command (UN) advance towards the Yalu River which had occurred after their intervention in the wake of the North Korean invasion of South Korea at the start of the war. The battle was fought between British and Australian forces from the 27th British Commonwealth Brigade with American armour and artillery in support, and the PVA 117th Division of the 39th Army, around the village of Pakchon on the Taeryong River. After capturing Chongju on 30 October the British and Australians had been ordered to pull back to Pakchon in an attempt to consolidate the western flank of the US Eighth Army. Meanwhile, immediately following their success at Unsan against the Americans, the PVA 117th Division had attacked southward, intending to cut off the UN forces as they withdrew in the face of the unexpected PVA assault. To halt the PVA advance, the 27th British Commonwealth Brigade was ordered to defend the lower crossings of the Taeryong and Chongchon rivers as part of a rearguard, in conjunction with the US 24th Infantry Division further upstream on the right.
Links: a. 117th Armed Police Mobile Division b. Eighth United States Army c. Battle of Chongju (1950) d. Pakchon County
d