Question

Given A = {a, b, c}, how many subsets does A have including ∅?
a. 4
b. 7
c. 8

Answer 1

A set of n elements has $2^n$ subsets.

There are 3 elements in the set A, so the number of subsets is $2^3=8$

You can write them out:
$\{\{\}, \{a\}, \{b\}, \{c\}, \{a, b\}, \{a, c\}, \{b, c\}, \{a, b, c\}\}$