Which one of the following statements is true?

a. neither chemical nor physical changes involve a change in appearance.
b. both chemical and physical changes can involve a change in appearance.

c. only chemical changes involve a change in appearance.

d. only physical changes involve a change in appearance.

the amount of current in the coil

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.