In the aftermath of an intense earthquake, the earth as a whole "rings" with a period of 56.8 minutes. what is the frequency of this oscillations?

The frequency is defined as the inverse of the period (time):

  (1)

And according to the International Units System its unit is Hertz ().

This means we have to convert this quantity given in minutes to seconds before solving the equation:

  (2)

Substituting (2)in (1):

Finally:

yup its correct its: c) b b

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.