Step 1: Understanding 'Bold'.
'Bold' means courageous, daring, or confident.
Step 2: Considering antonyms.
(A) Timid — shy/fearful; direct opposite.
(B) Never — adverb; unrelated.
(C) Sweat — noun/verb; unrelated.
(D) Small — size; not antonym of courage.
Step 3: Conclusion.
The correct antonym of 'Bold' is 'Timid'.