An airplane travels 70 miles per hour. The magnitude of the resultant velocity of the plane is 90 miles per hour, if it encounters a 20 mile per hour headwind.

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.

it would be kevlar ^^

b.a device that inputs heat into a cool object