A series of green flashes directed at an aircraft means respectively in flight on the ground
Why this is the answer
Per the TC AIM tower light signals, a series of green flashes means “return for landing” to an aircraft in flight and “cleared to taxi” to one on the ground. A steady green — not flashes — is the actual clearance to land.
Reference
TC AIM-RAC – Visual Signals TC AIM-RAC – Visual Signals
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.