Suppose you have a machine which has a very strong magnet inside. You have some computer disks in the room and, although you think they are far away enough from the magnet to be safe, you don$$t want to take any risks. What material would be appropriate for building a magnetic shielding enclosure?

$$A$)$ aluminum.

$$B$)$ plastic.

$$C$)$ iron.

$$D$)$ copper.