Which statement is true?
ACRT is a higher-level respiratory therapy certification.
Every CRT is also an RRT.
ARRT is a certification that adds a specialization.
Every RRT is also a CRT.

answer; ///(b) it is composed of four protein chains and four heme groups;

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.