int matrix[3][3] = { {1,2,3}, {4,5,6}, {7,8,9} }; int second_row[3] = matrix[1]; // accesses the second row of the matrixIn this example, we have declared a 3x3 matrix and initialized it with integers. We then access the second row of the matrix and store it in the array second_row. The resulting array should now contain the values {4,5,6}. The package library that contains functions for matrix operations such as initializing, accessing, and manipulating rows is likely a linear algebra library, such as the Eigen library or the Armadillo library. These libraries provide efficient and optimized functions for performing matrix operations, making it easier for developers to work with matrices in their code.