Answer
a. Elements and compounds
b. elements
c. elements
d. compounds
Work Step by Step
One red and one grey sphere bond together to make a compound. In addition, there are also red spheres that do not bond to anything.
There are only red spheres and they're not bonding to one another.
There are red and grey spheres but they are not bonding together
Two red and one grey sphere bond together to make a compound
