Which of the following is a subspace of R2\mathbb{R}^2R2?
The set of all points on the line y=xy = xy=x
The set of all points on the line y=x+1y = x + 1y=x+1
The single point {(0,0)}\{(0, 0)\}{(0,0)}
The first quadrant (x≥0,y≥0x \ge 0, y \ge 0x≥0,y≥0)