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: When did the expedition that John Colter was apart of in 1807 begin? Passage:Europeans may have ventured into the northern sections of the state in the late 18th century. Most of the southern part of modern-day Wyoming was nominally claimed by Spain and Mexico until the 1830s, but they had no presence. John Colter, a member of the Lewis and Clark Expedition, was probably the first American to enter the region in 1807. His reports of thermal activity in the Yellowstone area were considered at the time to be fictional. Robert Stuart and a party of five men returning from Astoria, Oregon discovered South Pass in 1812. The route was later followed by the Oregon Trail. In 1850, Jim Bridger located what is now known as Bridger Pass, which was later used by both the Union Pacific Railroad in 1868, and in the 20th century by Interstate 80. Bridger also explored the Yellowstone region and like Colter, most of his reports on that region of the state were considered at the time to be tall tales. During the early 19th century, fur trappers known as mountain men flocked to the mountains of western Wyoming in search of beaver. In 1824, the first mountain man rendezvous was held in Wyoming. The gatherings continued annually until 1840, with the majority of them held within Wyoming territory.
Links: a. Oregon Trail b. Robert Stuart (explorer) c. Rocky Mountain Rendezvous d. Lewis and Clark Expedition
Output:
d