问题详情

According to paragraph 1, why is it difficult to determine when the first clipper ship was built？
A．The clipper predates written records by almost 75 years.
B．Sailors kept the details of their vessels tightly guarded secrets.
C．The clipper has no technical specifications that can be used to identify it.
D．The term "clipper" was originally used to describe a variety of ships.请帮忙给出正确答案和分析，谢谢！