Geometry

Question Analysis：
This concept question assesses understanding of how a full shape (like a triangle) is transformed during reflection across y = x.

Key Concept Explanation:
Each vertex undergoes the transformation (x, y) → (y, x).
The entire shape is flipped over a diagonal, maintaining size and angles.

Step-by-Step Solution：
Example:
Triangle with vertices A(2, 3), B(4, 1), C(3, 2)
After reflection: A′(3, 2), B′(1, 4), C′(2, 3)
→ The triangle flips across the diagonal line y = x

Option Analysis：
A. Not a rotation
B. No resizing — reflection keeps shape/size
C. ✅ Correct — diagonal flip by coordi...