Which combination of emergency warning devices satisfies the reflector requirement checked during a bus pre-trip inspection?

AAMVA CDL Manual Section 4.1.1, p.4-1

Breakdown protection equipment is what keeps a disabled bus from being rear-ended on a shoulder or dark roadway. Drivers need to know the exact quantities because inspectors and skills-test examiners check for them, and a missing or short-count set of reflectors can be treated as a pre-trip defect.