21. 某系統之動態方程式為 \(\dot{\mathbf{x}}(t) = \begin{bmatrix} -1 & 1 \\ 0 & -1 \end{bmatrix} \mathbf{x}(t) + \begin{bmatrix} 0 \\ 1 \end{bmatrix} u(t), y(t) = \begin{bmatrix} 1 & 2 \end{bmatrix} \mathbf{x}(t)\)，其中 \(\mathbf{x}(t)\) 為狀態向量，\(u(t)\) 為輸入，\(y(t)\) 為輸出；則其狀態轉換矩陣 ( state transition matrix ) \(\Phi(t) = ?\)
(A) \(\Phi(t) = \begin{bmatrix} e^{-t} & te^{-t} \\ 0 & e^{-t} \end{bmatrix}\)
(B) \(\Phi(t) = \begin{bmatrix} e^{-t} & 0 \\ 0 & e^{-t} \end{bmatrix}\)
(C) \(\Phi(t) = \begin{bmatrix} e^{-t} & e^{-t} \\ 0 & e^{-t} \end{bmatrix}\)
(D) \(\Phi(t) = \begin{bmatrix} e^{-t} & t \\ 0 & e^{-t} \end{bmatrix}\)