In this question there are several information's of immense importance already given.
The number of pair of gloves that the merchant bought = 30 dozens
1 dozen = 12 gloves
Also
1 pair = 2 gloves
Then
The total numberof individual gloves bought
by the merchant = 30 * 12 * 2
= 720
The correct option among all the options given in the question is option "C" and it can be checked via the above solution.