Multiple Choice, Single Answer
1 questions. Answer them all, then submit once for your section score.
Read the passage and answer the question.
The modern elevator industry rests on a safety innovation rather than a mechanical one: the automatic brake. Elevators existed for centuries before their public debut at an 1854 exhibition, where an inventor demonstrated a platform that would not fall even if its supporting rope were cut. This device, not the motor or the cable, is what made tall buildings commercially viable, since tenants would not otherwise trust an elevator with their lives. Today's industry is dominated by a small number of multinational manufacturers who profit less from installing new elevators than from servicing existing ones, since maintenance contracts, often spanning decades, generate more reliable revenue than the one-time sale of equipment.