We know that the periodic table is organized into three main categories: metals, nonmetals, and metalloids. Identify which element below is incorrectly classified as a metal, nonmetal, or metalloid.
a. antimony (Sb) - metalloid

b. strontium (Sr) - metal

c. cerium (Ce) - metal

d. selenium (Se) - metalloid

e. rhodium (Rh) - metal

f. krypton (Kr) - nonmetal