Avoiding wake turbulence is
Why this is the answer
Per TC AIM-AIR (Wake Turbulence), avoiding wake turbulence is solely the pilot's responsibility. ATC may issue a caution, but the decision to accept a takeoff or approach behind a heavier aircraft, and how to fly it, rests entirely with the pilot-in-command.
Reference
TC AIM-AIR – Wake Turbulence / Considerations
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.