 If \(X,Y\in \mathcal{A}\) and \(X\in \mathbf{C}(\mathcal{A})\), then for all \(\mathcal{B}\), if \(X\in \mathcal{B}\), and \(Y\in \mathbf{C}(\mathcal{B})\), then \(X\in \mathbf{C}(\mathcal{B})\)   (WARP) 