Answer:
Mike is concerned about Dan's strategy because the source Dan is resorting to does not sound reliable.
Step-by-step explanation:
What may make Dan's source unreliable in Mike's opinion? The fact that the encylopedia is run by a company and not a univeristy ; or any other academic institution. Besides, Dan says he has never heard about it before. If Dan has not got any background information about the source, he should get some before using that source. If Dan learns that the " company" works along some university or any other academic institution, then, it may be a reliable source.