Question

a secondary source is most likely reliable and credible if it is:

Answer 1

A secondary source is most likely reliable and credible if it is written by someone who has a stable relation history in the field of the question.
And somewhat pertains to a more reliable source. 

Hope this helps. c:

Answer 2

                      This is what I believe would be the correct answer:
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"A secondary source is more likely to be reliable and credible if it's created by an educated expert and published by an academic journal"