Why does th e heart automatically adjust the flow to match activity levels? a. extreme actvity damages blood cellsand the body needs replacements b. the heart requires more oxygen when excersing c. it builds upahigher level of oxyge int he blood d. organs and musclesrequire moreblood under stress

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.