Which preventive contingency control does NIST specify with placement both above and below the computer room?

Answer: C. Water sensors

SP 800-34r1's preventive controls list names fire and smoke detectors and water sensors placed in the computer room ceiling and floor, catching water from above and from beneath the raised floor.

Source: NIST SP 800-34 Rev. 1 (NIST) — Sec. 3.3 Identify Preventive Controls