四六级考试

【单选题】 George Valensi's patent lasted until 1971 because ______.
A．there were not enough TV stations to provide color programs
B．the color TV receiver was not available until that time
C．nobody would offer any reward for his patent prior to that time
D．his patent could not be put to use for an unusually long time

网考网参考答案：D
网考网解析：
[解析] 文章第三段提到：“迄今为止所批准延长最长期限的是授予Ceorge Valensi的专利。他的1939年的彩电接收机线路专利延长到1971年，因为在这项专利正常有效期的大部分时间里，其发明没有获得收益的希望。” 查看试题解析出处>>