Answer:
B). Gold in California ignited interest in a railroad to reach the West. However, Americans disagreed on where to build the railroad.
Step-by-step explanation:
Transition words are demonstrated as the words that reflect the relation or connection between phrases or sentences and aids to offer a connected thought. It aids to prevent abrupt disconnection and keeps the flow of ideas intact among the sentences.
In the given sentence, option B as mentioned above proposes a unified meaning to the sentence through the use of transition word 'however'. The assertion includes that "Gold in California ignited interest in a railroad to reach the West" but "Americans disagreed on where to build the railroad" which could best be connected through the transition 'however' as it comprehends the meaning of the sentences by aptly linking two thoughts together. Thus, option B is the answer.