The activists’ energetic work in the service of both woman suffrage and the temperance movement in the late nineteenth century (i)__________ the assertion that the two movements were (ii)__________.
The words energetic work, which work as a specific indication how the work was AND provides a context of the quality of the support to the woman at the time, make our sentence or TOTALLY positive or TOTALLY negative.
I.E. the first and second blanks must go in the same direction. OR the two movements were akin OR were, in contrast, each other.
Now, in the FIRST blank clearly, C is out of scope. So everything boils down to A or B. However, we said that the two blanks must go in the same direction BUT B does not have a counterpart in the second blanks.
So the answer must be undermins and inimical.