1. What he has said is undoubtedly right.
    他所说的毫无疑问是对的。

2. However, there are undoubtedly some wrong ways,
    然而，却毫无疑问地有几种错误的方法。

3. Undoubtedly, it's a good lesson to learn, maybe especially for sociologists.
    毫无疑问，这是值得学习的一课，对社会学家来说也许更是如此。