Children must make / a resolution of giving up at least / one of the bad habit / such as biting nails, getting up late, eating fast-food, etc.

A)
Children must make
B)
a resolution of giving up at least
C)
one of the bad habi
D)
such as biting nails, getting up late, eating fast-food, etc.

Correct Answer :   one of the bad habi


'At least one of the bad habit' refers to one bad habit out of many bad habits. So, replace 'habit' with 'habits' in the sentence.