read rule 2

[JMN]

My take:

Blocking below the waist/illegal block (Rule 2-3-7) by A44.
This is not a chop block as it did not occur within the free blocking zone.

B's option to decline and give A a first down on the 50 or take the penalty from the point of the foul (assuming it was behind the 50)and repeat 1st down. It's a 15 yarder. Clock starts on the ready.