Explanation:

Correct Answer is (c).The original sentence is erroneous.
Reason: The word ‘pincing’ should be replaced with ‘pincer’ to make the sentence correct. The term ‘pincer movement’ is used in reference to a situation involving pressure from two different sides or forces.
E.g.: We are now caught in the pincer movement of rising domestic costs and a rising exchange rate.
Moreover, the sentence does not imply that corporate is interesting. It is referring to what is of interest to the corporates.  Hence ‘corporate interest’ should be used in place of ‘interesting corporate’ to make the sentence grammatically correct.
Among the given choices, only option C replaces the given bold part most appropriately.
The sentence after replacement becomes:
A pincer movement of corporate interest and political pressure combined with regulatory overdrive has cramped the autonomy of the teacher.Option C is hence the correct answer.