The Lewis acid character of boron tri halides follows the order:

A

BCl$$_3$$ > BF$$_3$$ > BBr$$_3$$ > BI$$_3$$

B

BI$$_3$$ > BBr$$_3$$ > BCl$$_3$$ > BF$$_3$$

C

BBr$$_3$$ > BI$$_3$$ > BCl$$_3$$ > BF$$_3$$

D

BF$$_3$$ > BCl$$_3$$ > BBr$$_3$$ > BI$$_3$$