单选题 ______ 40 years ago, the book continues to be marketed, mass-produced, and challenged.
A. Being written B. As written
C. It was written D. Though written

【正确答案】 B
【答案解析】本题测试分词用法。句子的主语为书，书是40年前被写出来的，故排除A和C。D选项的though一般不用在句首。