Intentional foul question

[Nevadaref]

Since this intentional foul occurred during a live ball, it is a personal foul. Therefore, you use the rule on attempting personal foul free throws.

RULE 8
SECTION 2 ATTEMPTING PERSONAL-FOUL FREE THROWS
The free throw(s) awarded because of a personal foul shall be attempted by the offended player. If such player must withdraw because of an injury or disqualification, his/her substitute shall attempt the throw(s) unless no substitute is available, in which case any teammate may attempt the throw(s) as selected by the team captain or head coach.


In your case this means B1 is the proper shooter.