Which is a rapid-acting insulin with an onset of action of less than 15 minutes?

Choice A reason: Insulin glargine is a long-acting insulin with an onset of 1–2 hours, providing basal coverage for 24 hours. It does not act rapidly to control postprandial glucose, unlike rapid-acting insulins, making this choice incorrect for the question. Choice B reason: Insulin detemir is a long-acting insulin with an onset of 1–2 hours, used for steady glucose control. It lacks the rapid onset (<15 minutes) required for immediate postprandial glucose management, making this choice incorrect. Choice C reason: Insulin aspart is a rapid-acting insulin analog with an onset of 10–15 minutes, peaking in 1–3 hours. It mimics the body’s insulin response to meals, effectively controlling postprandial glucose, making this the correct choice. Choice D reason: Regular insulin has an onset of 30–60 minutes, slower than rapid-acting insulins. It is used for short-term glucose control but does not meet the <15-minute onset criterion, making this choice incorrect.