Remember opposites attract and same charges repel each other.
Object A= negatively charged.
Object A and B attract so B must be positively charged.
Object B and C repel so because B is positively charged C must also be positively charged.
Object C and D attract and because C is positively charged, D must be negatively charged.
That is the answer to your problem
To help pick to up the metal and place it in a incinerator <span />
1) Constant speed
2) Slowing down
3) Not moving
4) Speeding up