Correct option is A
Option (a) is the correct idiom for the given context.
Given Idiom: Once bitten twice shy
Meaning: Someone who has been hurt or who had something go wrong will be far more careful the next time.
Example: After losing money in a risky investment, he's once bitten, twice shy about investing again.
Other idioms: ·
Bitten by the bug: suddenly enthusiastic about something ·
Bite off more than one can chew: to take on more responsibility than one can manage