Which of the following is a linear function? an xy coordinate plane is drawn. a parabolic curve that opens to the right is drawn. the vertex of the curve is on the axis. an xy coordinate plane is drawn. an ellipse is drawn on the axis and partially cutting the y-axis. an xy coordinate plane is drawn. a straight line going to left of the origin from the third quadrant to the first quadrant is drawn. an xy coordinate plane is drawn. a straight line starts from the origin and slants down to a certain point in the first quadrant, then is horizontal, and then slants down. all the line segments are straight lines in the first quadrant.