Can anyone tell me what’s a transplant is

A heart transplant is a surgery in which doctors remove a person's sick heart and replace it with a healthy donor heart. ... They choose to donate the organs because they want to help someone else who is sick.

Here's another example:

Mayo Clinic is the largest integrated transplant provider in the United States. Mayo Clinic has pre-eminent adult and pediatric transplant programs, offering heart, liver, kidney, pancreas, lung, hand, face, and blood and bone marrow transplant services. 

Have a nice day!

i think your answer is c. measurement system in which the medication dosage was calculated.