Please help.
In which statement is the transition used correctly?

Select one:

a. Gold in California ignited interest in a railroad to reach the West. As a result, Americans disagreed on where to build the railroad.

b. Gold in California ignited interest in a railroad to reach the West. However, Americans disagreed on where to build the railroad.

c. Gold in California ignited interest in a railroad to reach the West. Therefore, Americans disagreed on where to build the railroad.

d. Gold in California ignited interest in a railroad to reach the West. Before this, Americans disagreed on where to build the railroad.