Which statement best explains why the transcontinental railroad took several years to build?
(a)digging through the mountains was very difficult, and the long winters hampered workers’ ability to make progress.
(b)several civil war battles took place where the railroad was being built, so workers had to wait for the land to be clear and safe.
(c)a divided congress continued fighting over funding for the railroad, leading to work stoppages every few months.
(d)american indians engaged in frequent clashes with rail workers, so work stopped while safety measures were adopted.

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.

donald carl johanson (born june 28, 1943) is an american paleoanthropologist. he is known for discovering – with yves coppens and maurice taieb – the fossil of a female hominin australopithecine known as "lucy" in the afar triangle region of hadar, ethiopia.

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