Going through the given options A , B and E can be ruled out based on the following logic -
A : As much as , refers to quantitative comparison , whereas we are interested in the Number .
B : Twice as many as 1977 is incorrect as it gives the impression 2 times 1977.
C : Double what it , " It " is ambiguous , it might refer to clerks or female ministers and its not clearly specified.
E : Modifies the number of Clergies , whereas it must modify the Female ministers....
Hence C is correct..