The minimum flight visibility for VFR flight within a low level airway is
Why this is the answer
A low-level airway is controlled airspace, so the controlled-airspace VFR minimum applies: flight visibility of at least 3 miles (CAR 602.114(b); TC AIM-RAC). The lower 1- and 2-mile figures belong to uncontrolled airspace.
Reference
CARs 602.114 – Minimum Visual Meteorological Conditions for VFR Flight TC AIM-RAC – Control Zones, VFR Weather Minima
Question reproduced verbatim from Transport Canada’s PSTAR Study and Reference Guide (TP 11919E). The answer key is Transport Canada’s; the explanation is ours.
A study aid — not a substitute for the official guide, the CARs, or your instructor.