Which division of the nervous system has long preganglionic neurons?

Parasympathetic nervous system

Explanation:

Parasympathetic nervous system together with sympathetic nervous system is part of the autonomic nervous system. The autonomic nervous system also called the vegetative nervous system is part of the peripheral nervous system which inervates  smooth muscle and glands. Thus, it directly affects the function of internal organs and  regulates  functions such as the heart rate, digestion, respiratory rate,  urination etc. This nervous system control is  unconscious.

Parasympathetic nervous system works when organism is at rest so it is known as system responsible for "rest and digest functions". On the other hand, sympathetic nervous system works at active and stressful situations and it is known as "fight and flight" system.