An angle is in standard position and its terminal side lies on the negative $y$-axis. What is the measure of this angle in degrees?

• A. $180°$
• B. $107°$
• C. $253°$
• D. $270°$

Answer: (D)

Verified step by step guidance

1. Recall that an angle in standard position has its vertex at the origin and its initial side along the positive x-axis.
2. Identify the position of the terminal side: since it lies on the negative y-axis, it points straight down from the origin.
3. Understand that the positive x-axis corresponds to 0° (or 360°), and moving counterclockwise, the positive y-axis is at 90°, the negative x-axis at 180°, and the negative y-axis at 270°.
4. Therefore, the angle whose terminal side lies on the negative y-axis is measured as 270° in standard position.
5. Conclude that among the given options, the angle measure that corresponds to the terminal side on the negative y-axis is 270°.