Correct Answer: B
Explanation:
The sentence suggests that language is something very difficult to handle; it almost requires genius to handle it with skill. Therefore we choose two words that indicate ‘skill’ in effective use of language. Also the use of the word ‘subtle’ indicates that language is not obvious, and it is therefore hard to be precise - hence definiteness and certainty.
(aloofness = keeping apart, arrogant; alacrity= speed and eagerness; eloquence = ability to speak well)