The Matrix Below Describes What Kind of Covariance Structure in a Multilevel

Multiple Choice

The matrix below describes what kind of covariance structure in a multilevel model? $$\left( \begin{array} { l l l l } 1 & 0 & 0 & 0 \\0 & 1 & 0 & 0 \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{array} \right)$$

A) Unstructured
B) AR(1)
C) Diagonal
D) Variance components