Fat, fatter, fattest ; fastidious, more fastidious, most fastidious ; fast, ________ , ________.

 Key Points

• These are the comparative and superlative forms of adverbs.
• Adverb: fast
• Comparative:faster
• Superlative: fastest
• Adverbs that do not end in -ly comparative and superlative forms are identical to adjectives: add -er to form the comparative and -est to form the superlative. If the adverb ends in e, remove it before adding the ending.
  • for example:
  • He is the fastest among his friends. (Superlative)
  • They ran very fast.
  • Rohit runs faster than amit. (Comparative)

 
​As per the mentioned points above the correct answer is 'Option 3'