The correct option is
C About
Option A- By is used to indicate means, nearness, time, order, according to,
manner or instrument, measure, in the name of. Since this preposition
does not fit correctly in the given sentence, it is incorrect.
Option B- With is used to indicate means, possession, contents, relationship, for
and against. It does not fit the meaning of the sentence. Hence it is
incorrect.
Option C-Over indicates movement and position. Hence this is not the required answer.
Option D- About is used to indicate movement or position in various directions or places,in connection with,in connection with,near or nearby. In the given passage in connection with something is referred. Hence 'about' is the correct answer.