Answer: The correct option is (C) {1, 2, 3}.
Step-by-step explanation: We are given to select the option that gives the correct set notation.
We know that
The elements of a set are always written within curly brackets separated by comma.
For example, the set V of vowels in English Alphabet is written as follows :
V = {a, e, i, o, u}.
Therefore, from the given options, only the option (C) {1, 2, 3} is the correct set notation, because here the elements are written within curly brackets separated by commas.
Thus, (C) is the correct option.