Answer
Particle D created track 8.
Work Step by Step
The particle that created track 8 is known to have a seriousness quantum number of zero.
Then the particle that created track 8 is D or F.
D has a charge of -1 and F has a charge of 1.
According to the direction of curvature, only two other particles have the same charge as the particle that created track 8.
Thus the particle that created track 8 must have a charge of -1.
Particle D created track 8.
