This diagrams represents... a
a pure substance containing diatomic molecules
b
a pure substance containing compounds
c
a mixture containing compounds
d
a mixture of atoms

its A the first one

Explanation:

the first one

shield volcanos are angry and get mad over the smallest things so much that there heads erupt   pahoehoe and a'a lava. a composite volcano is the poller opposite of a shield volcano. its   peaceful thing and knows how to control its emotions.