**Core Concept**
The question requires understanding of medications used in the management of chronic obstructive pulmonary disease (COPD) and asthma, specifically those that relax airway smooth muscle.

**Why the Correct Answer is Right**
Bronchodilators are a class of medications that relax airway smooth muscle, leading to increased airflow and improved lung function. They can be further divided into three categories: beta-2 agonists (e.g., salbutamol, albuterol), anticholinergics (e.g., ipratropium bromide), and methylxanthines (e.g., theophylline). The correct answer is a medication that does not belong to these categories.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a medication that relaxes airway smooth muscle and is used in the treatment of COPD and asthma.
**Option B:** This option is incorrect because it is a medication that relaxes airway smooth muscle and is used in the treatment of COPD and asthma.
**Option D:** This option is incorrect because it is a medication that relaxes airway smooth muscle and is used in the treatment of COPD and asthma.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that bronchodilators can have systemic effects, such as tachycardia and tremors, due to their action on the beta-adrenergic receptors. This is particularly relevant when choosing a medication for a patient with a history of cardiac disease or anxiety disorders.

**Correct Answer: D. Morphine.**