Primary sources contain information a. with the advantage of hindsight and the perspective of an outside observer and may be more objective. b. on statistics gathered after an important historical event. c. provided by someone who's been through an event. it's a firsthand account that lends a unique perspective. d. on psychological information gathered from raw data from psychological tests.

If you're familiar with the phrase "second-hand," you probably know that second-hand information means that you heard it from somebody who heard it from somebody else. For example, if Jan told her friend Bob about something, and then Bob told you, you will have heard that story about Jan second-hand. In contrast, a primary source is a source who has first-hand knowledge of the event; it is from someone who was there. Thus, a primary source is C, a source that was "provided by someone who's been through an event. It's a firsthand account that lends a unique perspective." A journal or diary is a good example of a primary source. 

Hope should be your answer.