An object starts at 16 m/s with an acceleration of 4.5 m/s? How far does it go in 9.0 seconds?

wavelength variability is the right one

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.