Give some important and summary about Demagnetization magnets

When a magnetized magnet is exposed to a strong magnetic field that is set up in opposition to the magnet's magnetization, a portion of the magnet may become demagnetized. 

This demagnetization essentially reduces the magnet's effective field, and the magnet's performance suffers as a result.

The field strength required for the demagnetization must be of opposite polarity (reversing) to the magnetization field strength H sat, hence -H c. The demagnetization with reversing field H c only works on a magnetized material sample of simple, symmetrical geometry. Technical parts with irregular geometry and made of materials with different magnetic properties (for example hardened parts) must be demagnetized.

Explanation:

answer: a ball

explanation: because it will bounce

i think the answer is a, hope this : )