What happens when a metal bar is heated? A The distance between the molecules increases, making the bar longer.
B The molecules get larger, making the bar longer.
с The molecules vibrate more quickly, making the bar denser.
D The speed of the molecules increases, making the bar thinner.

When something is heated, its atoms vibrate. If one end of a metal bar is heated, the atoms at that end vibrate more than the atoms at the cold end. The vibration spreads along the bar from atom to atom. ... Metals are good conductors of heat.

Explanation:

d. learned preferences i believe is your answer

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.