题目内容：
AWe know the famous ones—the Thomas Edisons and the Alexander Graham Bells —but what about the less famous inventors? What about the people who invented the traffic light and the windshield wiper(雨刮器)？Shouldn’t we know who they are?
Joan Mclean think so. In fact, Mclean, a professor of physics at Mountain University in Range, feels so strongly about this matter that she’s developed a course on the topic. In addition to learning “who”invented”what”, however, Mclean also likes her students to learn the answers to the”why” and ”how” questions. According to Mclean,”When students learn the answers to these questions, they are better prepared to recognize opportunities for inventing and more motivated to give inventing a try.”
So,just what is the story behind the windshield wiper? Well,Mary Anderson came up with the idea in 1902 after a visit to Mew York City.The day was cold and stormy, but Anderson still wanted to see the sights ,so she jumped aboard a streetcar. Noticing that the driver was struggling to see through the snow covering the winshield,she found hersefe wondering why there couldn’t be a buolt-in devic for cleaing the window. Still wondering about this when she returned home to Birmingham, Alabama, Anderson started drafting out solutions. One of her ideas, a lever(操作杆)on the inside of a vehicle that would contral an arm on the outside, became the first windshield wiper.
Today we benefit from countless inventions and innovations，It’s hard to imagine driving without Garrett A.Morgan’s traffic light. It’s equally impossible to picture a world without Katherine J.Blodgett’s innovation that makes glass invisible, Can you picture life without clear windows and eyeglasses?
By mentionong “traffic light”and “windshield wiper”,the author indicates that countless inventions are__________.
A. beneficial,because their inventors are famous
B. beneficial,though their inventors are less famous
C. not useful, because their inventors are less famous
D. not useful, though their inventors are famous
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