Which of the following is an example of an empty set?
{x∈R:x2=−1}\{x \in \mathbb{R} : x^2 = -1\}{x∈R:x2=−1}
{x∈Z:1<x<2}\{x \in \mathbb{Z} : 1 < x < 2\}{x∈Z:1<x<2}
{0}\{0\}{0}
{∅}\{\emptyset\}{∅}