An ATC clearance
Why this is the answer
Unlike an instruction, a clearance is an authorization the PIC may accept or decline; under CAR 602.31(1) it becomes binding only once accepted. Accept it and you must comply — it is not automatically mandatory the way the 'same as an instruction' trap suggests.
Reference
CARs 602.31 – Compliance with Air Traffic Control Instructions and Clearances TC AIM-RAC – ATC Clearances, Instructions and Information
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.