Match the symbol used in DFD with their function.

In Data Flow Diagram (DFD) notation, a small set of shapes each carries a fixed meaning: a closed rectangle marks an External Entity — a source or sink of data that lies outside the system boundary; a pair of parallel lines (an open-ended box) marks a Data Store, where data is held between processes; a circle marks a Process that transforms incoming data into outgoing data; and the remaining D-shaped icon denotes Output, the point where processed data is delivered out of the system, once the other three icons are matched to their standard roles. (The numbers 1-4 and letters i-iv below are the figure's own reference labels for the icons and functions — not the positions of the answer choices.)

Applying this convention to the four icons in the question:

Checking the full assignment — 1-iv, 2-iii, 3-i, 4-ii — shows each of the four functions (i, ii, iii, iv) used exactly once, a valid one-to-one match. This confirms the assignment is internally consistent with the convention established above.