Answer:
C. an article in a journal written by two professors
Step-by-step explanation:
The source will be relaible because a research paper has to be written. A journal is a magazine meant to be read by researchers, teachers and students . This is so because they are generally published by universisties or organizations in charge of doing research. The articles from a journal are written , then, by scholars. In the example given, the article has been written by two professors. The fact that there are two writers makes the information even more reliable.