1. Parallelogram:
In a quadrilateral ABCD, if AB || CD, then the opposite sides AB and CD are parallel. This is one of the properties of a parallelogram. A parallelogram is a quadrilateral in which both pairs of opposite sides are parallel.
2. Explanation:
When two lines are parallel, it means they will never intersect no matter how far they are extended. In the case of quadrilateral ABCD, since AB || CD, it indicates that ABCD could be a parallelogram.
3. Rectangle:
A rectangle is a special type of parallelogram where all four angles are right angles. Just having AB || CD does not guarantee that ABCD is a rectangle unless additional information about its angles is provided.
4. Rhombus:
A rhombus is a special type of parallelogram where all four sides are of equal length. Again, without further information about the side lengths, it cannot be concluded that ABCD is a rhombus based solely on AB || CD.
5. Conclusion:
Given the information that AB || CD in quadrilateral ABCD, the shape can be identified as a parallelogram. However, without more details about the angles or side lengths, it cannot be definitively classified as a rectangle or a rhombus.
Therefore, the correct answer is (A) Parallelogram.

Parallelogram