The correct option is B minute
The word 'gargantuan' refers to something enormous.
Option A, negligible refers to something insignificant or unimportant.
Option B, bearable refers to something able to be endured.
Option C, minute refers to something extremely small.
Option D, minimal refers to something of a minimum amount, quantity or degree.
Thus, according to the meaning, the word 'minute' is the opposite of the word 'gargantuan'.