The correct answer is: Both A and R are true but R is not a correct explanation of A.
The Sultans of Delhi were appointed as Viceroys of the Caliph of Baghdad. This is true because the Caliph granted them recognition by way of khilat and khitab. However, this does not mean that R is a correct explanation of A. The Caliph granted recognition to the Sultans of Delhi for a variety of reasons, including their military power and their ability to maintain order in the region. The fact that the Caliph granted them recognition does not mean that they were his viceroys in the traditional sense. The Sultans of Delhi were independent rulers who owed allegiance to the Caliph but who were not under his direct control.
Option A is incorrect because R is not a correct explanation of A. Option B is incorrect because R is not the only reason why the Caliph granted recognition to the Sultans of Delhi. Option C is incorrect because R is true. Option D is incorrect because A is true.