How high should a fence be to stop a determined intruder?

A.
3 to 4 feet high

B.
6 to 7 feet high

C.
8 feet or more topped with barbed wire

D.
No fence will stop a determined intruder.

Explanation:
Most intruders will be discouraged by a tall fence topped with barbed
wire, but it should not be counted on to keep out serious intruders.