Concept:A quadrilateral is a closed two-dimensional shape made of four straight sides.
Explanation:A rhombus has four equal sides.
A parallelogram has four sides with opposite sides parallel.
A rectangle also has four sides and four right angles.
All three are quadrilaterals.
A triangle, however, has only three sides and three angles.
The prefix “tri-” means three, while “quad-” means four.
So a triangle does not fit the definition of a quadrilateral.
Answer:D. Triangle