What Is the Difference Between an MRI and an MRA

What is the difference between an MRI and an MRA?

A) an MRA scan is always a more extensive procedure that requires more time
B) an MRI scan is used to visualize organs, while an MRA scan is used to visualize vessels
C) an MRI does not use contrast material; an MRA uses contrast material
D) an MRI scan is used to visualize bones, while an MRA scan is used to visualize organs