Answer:
C. Statistical sources
Step-by-step explanation:
Searching information in reliable sources is the best way to support your research. When trying to identify whether a source is reliable or not you should check on the entity which emitted such information, its date of publication and author (if any). Also, when searching for information online, it is very important to take a look at the suffix of the website's link (those ending in .edu or .gov are the most reliable ones).