Aircraft flying VFR normally join the circuit at 1,000 feet AAE. This may not always be possible because of
Why this is the answer
Circuits are normally joined at 1,000 ft AAE, but a straight-in clearance, a NOTAM'd circuit altitude, or weather forcing a lower circuit can all change that (TC AIM-RAC, Traffic Circuits) — so any of the above applies.
Reference
TC AIM-RAC – Traffic Circuits – Controlled Airports
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.