The answers to these questions are:
1. In the first paragraph
a. He wants to convince readers that Buddhism is worth studying.
(This is explained when the author states that: No one can come into contact with the best that Buddhism offers ).
2. The passage implies that the author believes:
a) Adherents of the two religions can learn important things from one another.
(The clue to make this decision is when the author states: Buddhism in China undoubtedly includes among its adherents many high-minded, devout, and earnest souls who live an idealistic life. Christianity ought to make a strong appeal to such minds)
3. These arguments are related to: d. The book may be scholarly, but it is more affordable than most. (it is expressed in the first lines when the author states that A missionary no less than a professional student of Buddhism ...)
4. the intended audience of both the book and the book review
d. They are scholars
5. The author opinion is
c. It is better than the volumes written by other historians. Because of the writer experience.