When a body is moving in circular path at a distance r from its center, this is its velocity at any instant.

layer a is the exosphere and layer b is the thermosphere.   is the answer i think but i hope this .

the answer is b

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.