Let $A = \begin{bmatrix} a & b \\ c & d \end{bmatrix}$ be a $2 \times 2$ real matrix with $\det(A) = 1$. If the equation $\det(A - \lambda I_2) = 0$ has imaginary roots (where $I_2$ is the identity matrix of order $2$), then:

  • A
    $(a+d)^2 < 4$
  • B
    $(a+d)^2 = 4$
  • C
    $(a+d)^2 > 4$
  • D
    $(a+d)^2 = 16$

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