1. Classify calcium:

a. S = homogeneous mixture/solution
b. E = element
c. C = compound
d. HE = heterogeneous mixture

2. Classify pizza:

a. HE = heterogeneous mixture
b. E = element
c. C = compound
d. S = homogeneous mixture/solution

3. Classify carbon monoxide:

a. HE = heterogeneous mixture
b. C = compound
c. S = homogeneous mixture/solution
d. E = element