Some people believe that money can buy happiness. Dr. Goodwin wants to determine whether paying people plays a role in their happiness. The level of happiness would be considered to be the variable.

Answerfarmer's market; (b) would be my second choice

Unlike  ct scans, which use x-rays,  mri scans  use powerful magnetic fields and radio frequency pulses to produce detailed pictures of organs, soft tissues, bone and other internal body structures.  differences between  normal and abnormal tissue is often clearer on an  mri  image than a  ct.you can see more with a mri scan. for example on an mri you can see internal bleeding.