A flowchart is a graphical representation of an algorithm or process, and it uses a set of standardised symbols so that any reader can interpret the logic at a glance. Choosing the right symbol conveys the type of step being performed.

The commonly used flowchart symbols are:

• Diamond (rhombus): a decision — a point where a condition is tested and the flow branches, typically into Yes/No or True/False paths.
• Rectangle: a processing step or computation (for example, an assignment or arithmetic operation).
• Oval (or rounded rectangle): the terminal symbol marking Start and End (Stop).
• Parallelogram: an input/output operation such as reading data or displaying a result.
• Arrows (flow lines): show the direction in which control moves.

Because a decision requires the flow to split based on a condition, it is drawn as a diamond — the shape uniquely has multiple exit branches — making it the correct answer.

The parallelogram is wrong because it denotes input/output, not a branch. The oval is wrong because it marks the beginning or end of the flowchart. The rectangle is wrong because it represents a straightforward process step with a single entry and single exit, whereas a decision needs two or more outgoing paths.