A pilot who has donated blood should not act as a flight crew member for at least the next
Why this is the answer
Per TC AIM-AIR (Blood Donation), giving blood can disturb the circulation for several days, so a pilot who has donated should wait at least 48 hours before acting as a flight crew member. Generally, active pilots are advised not to donate blood at all.
Reference
TC AIM-AIR – Blood Donation
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.