Which of the following heights of fence deters only casual trespassers?

An 8-foot fence, especially when topped with barbed wire, is designed to deter highly determined intruders, far exceeding the casual trespasser threshold.

A height of 2 to 2.5 feet is too low to serve as a meaningful deterrent even for casual trespassers and is not a recognized security standard for perimeter fencing.

A height of 6 to 7 feet deters a broader class of intruders beyond casual trespassers, representing a higher security tier than the question specifies.

A fence height of 3 to 4 feet is the recognized standard for deterring only casual or unintentional trespassers - people who might wander in without deliberate intent. This low barrier provides a clear boundary marker but poses no real obstacle to a determined intruder, making it the threshold for casual deterrence in physical security frameworks.