**Core Concept**
Salmeterol is a long-acting β2-adrenergic receptor agonist (LABA) used in the management of asthma and chronic obstructive pulmonary disease (COPD). Its mechanism of action involves binding to the β2-adrenergic receptor, leading to smooth muscle relaxation and bronchodilation. However, this receptor activation can also have systemic effects, contributing to adverse effects.

**Why the Correct Answer is Right**
The correct answer involves understanding the systemic effects of β2-adrenergic receptor activation. Salmeterol can cause hypokalemia due to increased potassium excretion in the urine, which is mediated by the activation of β2-adrenergic receptors in the renal cortex. This leads to a decrease in serum potassium levels, potentially causing cardiac arrhythmias and other electrolyte imbalances.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a known adverse effect of salmeterol.
**Option B:** While salmeterol can cause tremors and nervousness, this is not the most significant or well-known adverse effect.
**Option C:** This option is not accurate; salmeterol is not associated with this particular adverse effect.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that LABAs like salmeterol can cause systemic effects beyond bronchodilation, such as hypokalemia, which requires careful monitoring and management in patients with cardiovascular disease or other underlying conditions.

**Correct Answer:** B. tremors