Which of the following in an orthogonal matrix `[6//7 2//7-3//7 2//7 3//7 6//7 3//7-6//7 2//7]` b. `[6//7 2//7 3//7 2//7-3//7 6//7 3//7 6//7-2//7]` c. `[-6//7-2//7-3//7 2//7 3//7 6//7-3//7 6//7 2//7]` d. `[6//7-2//7 3//7 2//7 3//7-3//7-6//7 2//7 3//7]`