Question

Prisons guarded by correctional officers on patrol and in gun towers, with electronic locking systems and massive concrete walls, are most likely to be ________ prisons.

Answer 1

They are most likely to be maximum-security prisons.
maximum-security Security prisons are specifically created to defend criminals that deemed to be really dangerous.
Such as the leader of Large crime syndicate, the perpetrator of mass killings, high-level terrorists, etc.