A Firm Has the Production Function F(x, Y)= X

A firm has the production function f(x, y) = x.₅ + y, where x is the amount of factor x it uses and y is the amount of factor y.On a diagram we put x on the horizontal axis and y on the vertical axis.We draw some isoquants.Now we draw a straight line on the graph and we notice that the slopes of all the isoquants that it meets have the same slope at the point where they meet this line.The straight line we drew was

A) vertical.
B) horizontal.
C) diagonal through the origin with slope 0.5.
D) diagonal with slope 2.
E) diagonal with slope greater than 2.