a is the name for a vertical column in the periodic table.\na family\nb period\nc subset
a is the name for a vertical column in the periodic table.\na family\nb period\nc subset
Answer
Brief Explanations:
In the periodic table, vertical columns are called families or groups. Elements in the same family have similar chemical properties. Periods are horizontal rows. A subset is a set - theoretic concept not related to the periodic - table structure.
Answer:
A. family