Which of the following are warning signs that a volcano will soon erupt? animals begin to act weird the sky darkens smoke coming out of the top of it the ground swells or vibrates water level and water temperature increase

I would say "The ground swells or vibrates."

Animals may also begin to act weird.

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.

the entire statement is true and correct.  

there's no diagram, nothing is illustrated, and no question is asked.