Which dependent clause could be added to the beginning of the sentence to indicate a cause and effect relationship? Mark Twain gained education through experience in the world.

A. Instead of attending school for a long time,
B. While he was a writer,
C. Because his father passed away,
D. When he was an adult,

Among the first American settlers in the West, the Whitmans played an important role in opening the Oregon Trail and left a tragic legacy that would continue to haunt relations between whites and Indians for decades after their deaths.

Marcus and Narcissa Whitman were both from upstate New York. Narcissa Prentiss was born in 1808 in Prattsburgh, New York, into a devout Presbyterian family. She was fervently religious as a child, at age sixteen pledging her life to missionary work. After she completed her own education, she taught primary school in Prattsburgh. In 1834, still awaiting the opportunity to fulfill her pledge, she moved with her family to Belmont, New York.

Marcus Whitman was born in 1802 at Rushville, New York. After studying under a local doctor, he received his degree from the medical college at Fairfield, New York, in 1832. He practiced medicine for four years in Canada, then returned to New York, where he became an elder of the Presbyterian church. In 1835 he journeyed to Oregon to make a reconnaissance of potential mission sites.

Shortly before Marcus' trip westward, Narcissa had also volunteered her services to the American Board of Commissioners for Foreign Missions, the umbrella group for Protestant missions to Indian peoples. The Board, however, was unwilling to send unmarried women as missionaries. After Marcus visited the Prentiss family for a weekend, the couple -- who may have had a passing acquaintance beforehand -- agreed to be married, and the Board in turn offered them positions as missionaries.

In 1836 the Whitmans headed West with another missionary couple, Henry Harmon Spalding (who had been jilted by Narcissa) and his wife Eliza, and with a prospective missionary named William H. Gray. St. Louis was their departure point and Oregon their ultimate destination. The group travelled with fur traders for most of the journey, and took wagons farther West than had any American expedition before them. Along the way, Narcissa and Eliza became the first white women to cross the Rocky Mountains. The Whitmans reached the Walla Walla river on September 1, 1836, and decided to found a mission to the Cayuse Indians at Waiilatpu in the Walla Walla Valley. The Spaldings travelled on to present-day Idaho where they founded a mission to the Nez Percé at Lapwai.

The Whitmans labored mightily to make their mission a success. Marcus held church services, practiced medicine and constructed numerous buildings; Narcissa ran their household, assisted in the religious ceremonies, and taught in the mission school. At first the couple was optimistic and seemed almost thrilled by the challenges their new life posed; Narcissa wrote home, "We never had greater encouragement about the Indians than at the present time." This optimism soon faded, however. The Whitman's two-year-old daughter drowned in 1839, Narcissa's eyesight gradually failed almost to the point of blindness, and their isolation dragged on year after year. Above all, the Cayuse continued to be unreceptive to their preaching of the gospel.

To the Cayuse, whose souls the Whitmans felt they were destined to "save," the mission was at first a strange sight, and soon a threatening one. The Whitmans made little effort to offer their religious message in terms familiar to the Cayuse, or to accommodate themselves even partially to Cayuse religious practices. Gift-giving was essential to Cayuse social and political life, yet the Whitmans saw the practice as a form of extortion. For the Cayuse, religion and domestic life were closely entwined, yet Narcissa reacted with scorn when they suggested a worship service within the Whitman household. Even a sympathetic biographer admits that "her attitude toward those among whom she lived came to verge on outright repugnance."

Because the Whitman's missionary efforts bore so little fruit, the American Missionary Board decided to close the mission in 1842 and transfer the Whitmans elsewhere. Marcus headed East, undaunted by the coming winter, in an ultimately successful effort to convince the board to reverse its decision. On his return journey in 1843, he helped lead the first "Great Migration" to the West, guiding a wagon train of one thousand pioneers up the Oregon Trail. Soon, the Whitmans were spending more time assisting American settlers than they were in ministering to the Cayuse. Childless since their daughter had drowned, they took in eleven children of deceased immigrants, including the seven Sager children whom they adopted in 1844. Their mission also served as a kind of boarding school for early Oregon settlers like Joe Meek, whose daughter lived there for a time.

I think the answer is D when he’s around adult adult