The correct answer is (c). The international boundary between North Korea and South Korea runs along the 38th parallel north. This line was established by the United Nations in 1945 to divide the Korean peninsula into two occupation zones, with the United States occupying the southern zone and the Soviet Union occupying the northern zone. The division was intended to be temporary, but it became permanent when the two countries were established in 1948. The 38th parallel is a heavily fortified border, and there is no civilian traffic across it.
The other options are incorrect. The 25th parallel north runs through the middle of the Korean peninsula, and the 33rd parallel north runs through the southern part of the peninsula. The 48th parallel north runs through the northern part of China.