Which of the following is a fish?

The characteristic features of fishes are aquatic, streamlined body with scales, 2-chambered heart and gills. Bombay duck, salmon and Hippocampus exhibit these features thus they belong to the class Pieces. Bombay duck or bummalo is a 'lizardfish'. It is native to the water between Mumbai and Kutch in the Arabian sea and a small numbers are also found in the Bay of Bengal.
Salmon is the common name for several species of fishes.