I believe the answer is: B. the shooting of an unarmed rider.
In the speech, there is a dark connotation that made by the speaker when he mentioned the shooting of unarmed riders who are not willing to conform to their orders. Especially to the lower ranks who are bound by the orders from higher officers.
The answer is gerund because golfing ends in ING
A. Accept
This is the best answer, 1 way to do this is to put each word in for the 'acknowledge' and see which one fits the best!
Hope this helps!