Which of these battery sizes is physically the largest?

Of the batteries listed the largest is the D battery. The D battery is cylindrical with an electrical contact at each end; the positive end has a nub or bump. They are typically used in high current drain applications, such as in large flashlights, radio receivers, and transmitters, and other devices that require an extended running time.

Historically the term "battery" referred to a collection of electrochemical cells connected in series; however, in modern times the term has come to refer to any collection of cells (or single cell) packaged in a container with external connections provided to power electrical devices, leading to the variety of standardized form factors available today.

Technical standards for battery sizes and types are published by standards organizations such as the International Electrotechnical Commission (IEC) and American National Standards Institute (ANSI).

The D Battery size is: 34.2 mm × 61.5 mm (1.35 inches × 2.42 inches)

The 9-volt Battery size is: 26.5 mm × 48.5 mm (1.04 inches × 1.91 inches)

The AA Battery size is: 14.5 mm × 50.5 mm (0.57 inches × 1.99 inches)

The N Battery size is: 12 mm × 30.2 mm (0.47 inches × 1.19 inches)