Agroup of astrologers has written a book about how to use the stars to you choose the right friends. this could be considered an example of a. pseudoscience because it is backed by scientific studies. b. pseudoscience because it involves beliefs, not facts. c. science because we can study the stars. d. science because it is based on beliefs.

pseu·do·sci·ence

/ˌso͞odōˈsīəns/

noun

a collection of beliefs or practices mistakenly regarded as being based on scientific method.

Astrology isn't based on facts and can't be tested.  

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.