Rational Number Space is Sigma-Compact

Theorem
Let $\left({\Q, \tau_d}\right)$ be the rational number space under the Euclidean topology $\tau_d$.

Then $\left({\Q, \tau_d}\right)$ is $\sigma$-compact.

Proof
From Rational Numbers are Countably Infinite, $\Q$ is countable.

Hence the result from definition of Countable Space is $\sigma$-Compact.