Select the word pair that best represents a similar relationship to the one expressed in the pair of words given below.
(The words must be considered as meaningful English words and must not be related to each other based on the number of letters/numbers of consonants/vowels in the word.)
Pleasure : Pain

The given word pair is "Pleasure : Pain", which represents a relationship of opposites (antonyms).
Analyzing the options:
A) Fast : Quick 
Incorrect because both words have similar meanings (synonyms), not opposites.
B) Gentle : Brutal

Correct because "gentle" and "brutal" are opposites (antonyms).
C) Smart : Intelligent 
Incorrect because both words mean the same (synonyms).
D) Angry : Furious 
Incorrect because "angry" and "furious" are similar in meaning (synonyms), not opposites.
Thus, the correct answer is option (b). ​​