## **Core Concept**
The question tests the knowledge of insulin preparations and their routes of administration. Insulin is a crucial hormone for glucose regulation, and its administration route can significantly affect its onset and duration of action. Different insulin formulations are designed for specific administration routes.

## **Why the Correct Answer is Right**
Regular insulin (option ) is the correct answer because it can be administered intravenously. This is due to its soluble form, which allows it to be mixed with other solutions for IV administration. Regular insulin has a rapid onset of action and a short duration of action, making it suitable for intravenous use, especially in critical care settings or during surgeries where tight glucose control is needed.

## **Why Each Wrong Option is Incorrect**
* **Option A:** (usually lente or ultralente insulin) is not suitable for intravenous administration. These are intermediate-acting and long-acting insulins, respectively, designed for subcutaneous injection.
* **Option B:** (usually NPH insulin) is also not suitable for intravenous administration. It is an intermediate-acting insulin used for subcutaneous injection.
* **Option D:** (usually insulin glargine or detemir) is not suitable for intravenous administration. These are long-acting insulins designed for subcutaneous injection.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that only regular insulin (and sometimes insulin aspart or lispro in specific protocols) can be safely administered intravenously. This is critical in intensive care units (ICUs) and during surgical procedures where glucose levels need to be tightly controlled.

## **Correct Answer: . Regular Insulin**