Question

read the excerpt from \elevator systems of the eiffel tower, 1889\ by robert m. vogel.
the first complete elevator machine in the united states, constructed in 1855, was a complex and inefficient contrivance built around an oscillating-cylinder steam engine. the advantages of an elevator system independent of the mill drive quickly became apparent, and by 1860 improved steam elevator machines were being produced in some quantity, but almost exclusively for freight service. it is not clear when the first elevator was installed explicitly for passenger service, but it was probably in 1857, when otis placed one in a store on broadway at broome street in new york.
in the decade following the civil war, tall buildings had just begun to emerge, and, although the skylines of the worlds great cities were still dominated by church
according to this excerpt, what was an underlying cause of increased steam elevator production?
○ construction of tall buildings
○ the need to move supplies in mills
○ an elevator in a store on broadway
○ commercial advantages

Explanation:

The text mentions that the advantages of an elevator system independent of the mill drive quickly became apparent, leading to increased production. This implies a commercial advantage (the benefit of having an independent elevator system) as the underlying cause. The construction of tall buildings is mentioned later (after the increase in steam elevator production for freight), the store elevator is an example of passenger use (not the cause of production increase for freight which was the initial increase), and the need to move supplies in mills was the initial use but the key is the advantage (commercial) of the independent system that led to more production.

Answer:

commercial advantages