Geometry

Question Analysis:
This question tests knowledge of angle properties in parallelograms.
The key is identifying which statement is not always true for all parallelograms.

Key Concept Explanation:
Opposite angles in a parallelogram are equal (A is true).
Adjacent angles are supplementary (B is true).
The sum of interior angles in any quadrilateral is 360° (D is true).
Only rectangles (a type of parallelogram) have all right angles, so C is not a general property.

Step-by-Step Solution:
Recall the definition of a parallelogram (opposite sides parallel and equal).
Review angle properties:
Opposite angles = equal.
Adjacent angles = supplementary (add to 180°).
Eliminate A, B, and D as standard properties.
Recognize that C is only true for rectangles, not all parallelograms.