D, C , and B will die in this order
D dies first * by the time red ball get to D, it will be in the same position as it was when it was static, remember the slope is at 90 degree angle from the red ball, the red ball is 360 degree circle, its going to have exactly 1 full spin on the slope to the to D.
*Don't even think about the small space inside the red circle face upwards will save D . is at 180 degree and the slope is at 90 degree angle, the small space will be facing upwards, same position it was when it was static, this rules out any chances of D getting lucky to survive this death riddle, its going to be the direct opposite side that kills D
C dies when the spikes under the see-saw thrust from the drop(weight) of the red ball will play a major role in this
B dies when the blue ball goes over the ledge * the red ball will have speed and force and left direction ,its going to move the same direction after hitting the see-saw, it going to catapult the blue ball when the red ball hits the see-saw... remember the small ledge have an angle that slopes left upwards towards B
A will survive because the ledge between him and B is much taller
Notice: one thing i do find very odd, the blue should be between the see-saw and ledge in order for the ball to be catapulted in the direction of B. if the ball is between the pivot of the see-saw and the ledge, for B to die, the wight of the red ball will have to be greater than that of the blue ball.
Can you explain the position of the blue well?