What feature is labeled b in figure 7 - 1

Terminal moraine

Explanation: Terminal moraine is a type of glacial depositional feature which are formed due to the movement of glaciers, along with the particles and debris that are plucked and carried away to the furthest point. This particles then gets deposited after the melting of the ice. It is the maximum distance that glacier moves.

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.