Classify each of the following elements as a metal, a nonmetal, or a metalloid:
boron, carbon, aluminum, and silicon.

Silicon is neither metal nor non-metal; it's a metalloid, an element that falls somewhere between the two. The category of metalloid is something of a gray area, with no firm definition of what fits the bill, but metalloids generally have properties of both metals and non-metals.

Explanation:

The non-metals are boron and carbon. The metal is aluminum and the metalloid is silicon.

Explanation:

non-metal = boron, carbon

metal = aluminum

metalloid = silicon

the answer is c.the valence of the atoms combine .