One who knows two languages:
A
Bigot
B
Bigamy
C
Bilingual
D
Brittle
Correct Answer: Bilingual
The one word substitution is Bilingual.Bigot : a person who is a blind supporter of his religion.
Bigamy : the offence of marrying someone while already married to another person.
Brittle : hard but liable to break easily.
Bilingual : speaking two languages fluently.