Goaltending?

[actuary77]

Which of the following (if any) are goaltending situations?

(a) A1 makes a shot. The ball is in its downward motion (but not yet hit the rim) and B1 taps the backboard.

(b) A1 makes a shot. The ball has hit the rim and has not entered the basket, but there is a legitimate chance that it will. B1 taps the backboard.

(c) Same as situation (a) but A2 is the one that hits the backboard.

(d) Same as situation (b) but A2 is the one that hits the backboard.

Note that in all the above situations, neither the ring or net was touched.

Is the call clear cut or is it a judgement situation on whether the tap was hard enough to maybe move the backboard and alter the shot?