The correct answer is answer A ("Review or summary").
In a preface or abstract you might be able to understand what an author's purpose is but probably not their viewpoint until you read on.
The bibliography will give credibility to the source and help you recognize what kind of material it aligns with, but it has nothing to do with purpose or viewpoint.
Finally, the conclusion has more to do with viewpoint than purpose, and will be more focused on contrasting initial thoughts with final thoughts after studying a topic.
In order to get a better idea of what a source's purpose and viewpoint is, I'd read a summary or review. This generally entails a more detailed yet brief overview of a source's content in its entirety, which is what you're looking for.
Hope this helps!