Given the task definition and input, reply with output. In this task, you're given a question, along with a context passage which has extra information available on certain terms mentioned in it. Your job is to determine which sentence(s) from the passage can be used to search for further information needed to answer the question.

Question: Which river that trappers assembled pack trains at the junction of is longer? Passage:The Bad Pass Trail, also known as the Sioux Trail, was established by Native Americans on the border of present-day Montana and Wyoming as a means of access from the Bighorn Basin in Wyoming to Bison-hunting grounds in the Grapevine Creek area of Montana. Marked by stone cairns, the trail led across Bad Pass and was established in pre-Columbian times. After Europeans arrived in the area it was frequented by fur trappers and mountain men, beginning in 1824. Trappers assembled pack trains at the junction of the Shoshone River and the Bighorn River, using the Bad Pass Trail to avoid Bighorn Canyon. The trail ended at the mouth of Grapevine Creek on the Bighorn, from which the pack train could float down the Bighorn on rafts to the Yellowstone River and then to the Missouri and on to St. Louis.
Trappers assembled pack trains at the junction of the Shoshone River and the Bighorn River, using the Bad Pass Trail to avoid Bighorn Canyon