**Core Concept**
Insulin preparations vary in their onset and duration of action, which is crucial for managing diabetes mellitus. Rapid-acting insulin analogs have a shorter onset and duration of action compared to regular human insulin.

**Why the Correct Answer is Right**
Rapid-acting insulin analogs, such as insulin aspart, insulin glulisine, and insulin lispro, have a faster onset of action (within 15 minutes) and a shorter duration of action (3-4 hours) compared to regular human insulin. This allows for more precise control of postprandial glucose levels. The rapid onset and short duration of action are due to the alteration of the insulin molecule, which affects its absorption and degradation rates.

**Why Each Wrong Option is Incorrect**
**Option A:** Regular human insulin has a moderate onset of action (about 30-60 minutes) and a duration of action of around 6-8 hours, making it not a rapid-acting insulin.
**Option B:** Insulin glargine is a long-acting insulin analog with a slow onset of action and a prolonged duration of action (up to 24 hours), so it is not rapid-acting.
**Option C:** Insulin detemir is another long-acting insulin analog with a slow onset of action and a prolonged duration of action (up to 24 hours), making it not rapid-acting.

**Clinical Pearl / High-Yield Fact**
When prescribing insulin, it is essential to consider the patient's lifestyle, dietary patterns, and activity levels to optimize insulin dosing and timing.

**Correct Answer:** B. Insulin glargine