Geometry

Question Analysis:
This question tests basic conceptual understanding of vertical reflections.
The main focus is identifying which coordinate remains unchanged.

Key Concept Explanation:
A vertical line goes up and down (like x = 2)
Reflecting across a vertical line flips the point left or right
So the x-coordinate changes
The y-coordinate stays the same

Step-by-Step Solution:
Imagine reflecting (3, 5) over the vertical line x = 1
The new x would change, but y stays 5
This proves that y-coordinate is unchanged

Option Analysis:
A. ❌ The x-coordinate does change
B. ✅ Correct — y stays the same
C. ❌ Only one coordinate changes, not both
D. ❌ No diagonal movement happen...