Option: (A)Digging through the mountains was very difficult, and the long winters hampered workers’ ability to make progress.
Explanation:
The Transcontinental Railroad took several years to build because of its geographical condition which made the region harsh than the East. Railroad shortened travel time between the East and West. It took several years because ever work was done by the workers with their hand. Cold winters slowed down the works in building the railroad. Building railroad was back-breaking work for the workers.
The statement that best explains why the transcontinental railrold took several years to build is digging through the mountains was very difficult, and the long winters hampered workers' ability to make progress. The foothills of Sierra Nevada, the winter snowtorms, shortage of reliable labor and increasing need for tunneling hampered the progress as they went higher in the mountains.
