The form of the linear equation is
y must have power 1 and also x mast have power 1
Let us check each answer
Since x and y have the power of 1, then
The graph of it is a line
Since x and y have the power of 1, then
The graph of it is a line
Since x and y have the power of 1, then
The graph of it is a line
Since x has a power of 2, then
The graph of it is not a line
The answer is D