**Core Concept:** Insulin analogues are modified forms of regular human insulin with altered amino acid sequences at the B chain, designed to enhance pharmacokinetic and pharmacodynamic properties for better glycaemic control in patients with diabetes.

**Why the Correct Answer is Right:** Roughly 90% of insulin analogues are designed to mimic human insulin, while the remaining 10% are analogues of animal insulins (e.g., pork or beef insulin). The correct answer, **D.** Humulin R (regular human insulin), is not an insulin analogue because it is derived from human pituitary glands and does not have any significant structural modifications.

**Why Each Wrong Option is Incorrect:**

**Option A.** Humulin NPH (N is for neutral protamine Hagedorn) is a protamine-stabilized insulin analogue with a longer duration of action than regular insulin. This makes it incorrect as well.

**Option B.** Humulin 70/30 (70% Humalog and 30% Humulin R) is a pre-mixed insulin analogue containing a rapid-acting insulin analogue (Humalog) and a regular insulin analogue (Humulin R), which makes it incorrect.

**Option C.** Levemir is a long-acting insulin analogue, not an insulin analogue.

**Clinical Pearl:** Structural modifications in insulin analogues may lead to differences in absorption, action, and duration of action compared to regular human insulin. This allows for more targeted glycaemic control.

**Correct Answer:** D. Humulin R (regular human insulin) is not an insulin analogue. It is derived from human sources and does not have significant structural modifications, making it different from insulin analogues that are designed for better pharmacokinetic and pharmacodynamic properties.