This diagram shows a transistor with the arrow on the emitter pointing outward. In transistor symbols, the arrow's direction indicates the type.

An arrow pointing out of the emitter represents an n-p-n transistor. The arrow shows the direction of conventional current flow, which is from the P-type base to the N-type emitter.

An arrow pointing in would represent a p-n-p transistor.

Therefore, the correct answer is an n-p-n transistor.