Three Pith Balls Supported by Insulating Threads Hang from a Support

Multiple Choice

Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that

A) Y has a negative charge.
B) Z has a negative charge.
C) Y has a positive charge.
D) Z has a positive charge.
E) Z is neutral (has no net charge.)