Which topic sentence fits the following paragraph? ... Men died on the cliffs when they failed to scramble out of the way before a blast or when the ropes to the
baskets broke. Men died in the tunnels when the nitroglycerin exploded without warning. Ah Goong was one
of the lucky ones; he lived to see the Central Pacific reach Promontory Point, Utah, where it joined the Union
Pacific to form the first transcontinental railroad in 1869. In the celebration that followed, orators basked in
the accomplishment of the "greatest monument of human labor," never mentioning the Chinese workers
whose prodigious labor had built the railroad.
- Roark et al., The American Promise: A History of the United States, Bedford/St. Martin's

Working on the Central Pacific Railroad was a dangerous and thankless job.
Ah Goong was a Chinese immigrant who helped build the Central Pacific Railroad.
Constructing the Central Pacific Railroad involved considerable labor and materials, but it paid off
for investors.
The Central Pacific Railroad stretched from California to Utah.