Can’t it be option B using the strategy that the first blank matches with just as believing and second blank matches countering the strength
The use of “just as” indicates that the first clause (about the past) and the second clause (about the present) express the same idea.
To summarize, the main idea: just as belief in astrology countered the strength of established churches in the past, it currently goes against (defies) the professional sciences.
Since astrology countered the strength of established churches (emphasis on the word “established”) in the past, it was not an established faith. The opposite of “established” would be “underground”. Choice (B) “accepted” does not contrast with “established”, but rather seems to be similar.
Additionally, if astrology currently goes against the professional sciences, then believing in astrology must be an act of “defiance against” the professional sciences.
Choice (C) is correct.