What would be the best method to separate only iron fillings from a mixture of sand, water, iron filings, and salt

the results is a decrease in air temperature with an increase of altitude.

explanation:

adding a(n) to an electric circuit would increase the magnetic field around a wire;

b. solenoid

a solenoid is a type of electromagnet whose purpose is to generate a controlled magnetic field.

if the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.