Answer:
The reason for which you might perform a subject search is the following one:
B) to look for general information on a topic.
Explanation:
When you perform a subject search, you find general information on a topic, that is, you find answers for overall questions regarding a particular subject: What is it? Where can you find it? Why is it done? Who is it aimed at?, etc.
Eg: Let's say you know little or nothing about Gothic Literature. If you perform a subject search on it, the first piece of info you will come across will be what it is and what the features of it are. Then, you will see names of authors, books, etc., that is, you will find general information on the topic.
