Final answer:
There is one location where a transportation route crosses the DMZ, which is the Gyeongui Line railroad connecting South Korea to the Kaesong Industrial Region in North Korea.
Step-by-step explanation:
The Demilitarized Zone (DMZ) between North and South Korea is one of the most heavily fortified borders in the world. While the DMZ itself is meant to be free of military installations and activities, it does allow for some controlled transportation routes to cross it. The answer to the question of how many locations there are where transportation routes cross the DMZ is B. One. There is a single transit route called the Korail's Gyeongui Line, which is a railroad that connects South Korea to the Kaesong Industrial Region in North Korea. Even though there is infrastructure for roads and additional railways, they are not currently in regular use for crossing the DMZ.