Geometry

Question Analysis:
This question involves understanding angles and diagonal behavior in a rhombus.
The main focus is on diagonal bisection and angle calculations.

Key Concept Explanation:
Diagonals in a rhombus are perpendicular.
They bisect the angles they connect to.
Opposite angles are congruent.

Step-by-Step Solution:
A: Diagonals in a rhombus are perpendicular → ✅
B: ∠CDA = ∠DAB only if it's a rectangle or square → ❌
C: Diagonal bisects ∠DAB → ½ × 40° = 20° → ✅
D: Diagonals in a rhombus bisect the angles they connect to.→ ✅
E: ∠DAB = 40°, so...