Which type of blood vessel normally contains valves to keep the blood flowing in One Direction a) arteries
b) veins
c) capillaries ​

B) Viens

The veins have valves to keep the blood pumping out and not coming back in the heart.

a axis of a graph is a color or shade so we can all go outside and have a party so we can eat   some grilled cheese sammiches and broccoli and have some ugly fun times

i don't know why i put this, i know its not the i was just bored : p

delete this answer while you can

i am going to guess that it is co2.