Explanation:

Fragment A: If the opposition want to base its.

The error is with respect to subject-verb disagreement.

Correct: If the opposition wants to base its

Fragment B: campaign in the mismanagement of

The opposition is using the mismanagement as a basis on which to run its campaign.

Correct: campaign on the mismanagement of

Fragment C: the economy and agriculture with

The mismanagement is being done by the governments.

Correct: the economy and agriculture by

Fragment D is correct.

Hence, option B is correct.