The correct option is (b) xq(n) = Q[x(n)] = \(\hat{x}_k\), if x(n) ∈ Ik
To explain: The possible outputs of the quantizer (i.e., the quantization levels) are denoted as \(\hat{x}_1, \hat{x}_2,…\hat{x}_L\). The operation of the quantizer is defined by the relation, xq(n) ≡ Q[x(n)]= \(\hat{x}_k\), if x(n) ∈ Ik.