Final answer:
A negatively charged object becomes grounded by losing electrons to another object, usually the Earth, thus reducing its negative charge or neutralizing it.
Step-by-step explanation:
The best explanation for how a negatively charged object can become grounded is that the object loses electrons to another object, which is usually the Earth in grounding scenarios. Grounding implies the presence of a conductive path that allows charge to transfer to the Earth, which has a virtually infinite charge capacity. Since electrons carry a negative charge, the loss of electrons from a negatively charged object to the Earth will make the object less negatively charged or neutral, depending on the number of electrons transferred.