Final answer:
The lifetime of an antineutron isolated from normal matter is expected to be seconds to minutes.
Step-by-step explanation:
The lifetime of an antineutron that is isolated from normal matter is seconds to minutes.
Antineutrons are highly unstable and undergo decay rapidly.
The half-life of a lone neutron, which is similar to an antineutron, is about 10.25 minutes, meaning that there is a 50% chance of survival over this period.
However, each half-life interval cuts the probability of survival in half again.