If a point lies on the y-axis, its x-coordinate is

1. The y-axis is the vertical reference line. 2. Points on it have no horizontal offset from the origin. 3. So their x-coordinate is 0. 4. Hence option A is correct. _Source: Selina Concise Mathematics Class 9, Ch 26 Co-ordinate Geometry (Mistral OCR'd PDF), section on axes_