The transportation by a raft is symbolic of the role of transportation in the evolution of local history. Paleo-Indians arrived about 12,000 years ago. The rich natural resources made the Sacramento Valley a "Garden of Eden." Permanent villages were established about 8,000 years ago. Native Americans walked and traveled the rivers and waterways with rafts. The later arriving Spanish entered the Valley by horse, British and American trappers entered by horse and on foot. Settlers from the Midwest and east coast arrived in wagon trains. Gold seekers walked over land along side wagons or by sea on sailing ships and later steamboats. By the late 1840's dreams of a transcontinental railroad were debated. In 1849 the "friends of a Rail Road to California” met in Boston to hear a proposal for a railroad from St. Louis to San Francisco. But the shorter transcontinental crossing at the Isthmus of Panama by a railroad would occur first in 1855. Meanwhile, the connection between San Francisco and Sacramento was improved by an expanding, fast, and efficient steamboat service. In 1856 the Sacramento Valley Railroad opened officially for service between Sacramento and Folsom.
Your research paper is entitled "Factors Improving Transportation in Sacramento Valley Area." Which sentence in paragraph 2 would be MOST helpful as evidence in your paper?

A) By the late 1840's dreams of a transcontinental railroad were debated.
B) The transportation by a raft is symbolic of the role of transportation in the evolution of local history.
C) But the shorter transcontinental crossing at the Isthmus of Panama by a railroad would occur first in 1855.
D) Meanwhile, the connection between San Francisco and Sacramento was improved by an expanding, fast, and efficient steamboat service.