A、They were common in the United States, but not in Europe. B、Only a few people had them. C、People considered them essential. D、

(16)I’m sure almost everyone of you looked at your watch or at a clock before you came to class today. Watches and clocks seem as much part of our life as breathing or eating.(17)Any yet, do you know that watches and clocks were scarce in the United States until the late 1850s. In the late 1700s people didn’t know the exact time unless they were near a clock. Those delightful clocks in the squares of European towns were built for the public.
    After all, most citizens simply couldn’t afford a personal timepiece.(18)Well, until the 1800s, in Europe and the United States, the main purpose of a watch, which by the way was off and on a gold chain, was to show others how wealthy you were. The word "wrist watch" didn’t even enter the English language until nearly 1900. By then, the rapid pace of industrialization in the United States meant that measuring time had become essential. How could the factory worker get to work on time, unless he or she knew exactly what time it was. Since efficiency was now measured by how fast the job was done, everyone was interested in time.(19)And since industrialization made possible the manufacture of large quantities of goods, watches became fairly inexpensive. Furthermore, electric lights kept factories going around the clock. Being "on time" had entered the language and life of every citizen.
16. What does the professor mainly discuss?
17. What was true of watches before the 1850s?
18. According to the speaker, why did some people wear watches in the 1800s?
19. What effect did industrialization have on watch making?