Which type of vessel normally contains valves that prevent the backward flow of materials

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

acceleration= v2-v1/t so 8m/s-3m/s / 3s =to 8/3 or

2.67 m/s^2

hope i

-lavira: )

wha is what i will use to get my free points