question: What is the condition for the secrecy capacity to be zero in the MIMO wiretap channel? option 1: If there are multiple positive generalized eigenvalues in the pencil formed by the product of the channel matrices, the secrecy capacity is zero. option 2: If there are no positive generalized eigenvalues in the pencil formed by the product of the channel matrices, the secrecy capacity is zero. option 3: If there are multiple negative generalized eigenvalues in the pencil formed by the product of the channel matrices, the secrecy capacity is zero. option 4: If there are no negative generalized eigenvalues in the pencil formed by the product of the channel matrices, the secrecy capacity is zero. option 5: If there is a zero generalized eigenvalue in the pencil formed by the product of the channel matrices, the secrecy capacity is zero. 