Okay, let's tackle this question. The user wants me to create a detailed explanation for a multiple-choice question about adverse effects of β2 agonists. First, I need to recall what β2 agonists are. They are drugs like albuterol, salbutamol, and terbutaline, used for asthma and COPD. Their main action is to relax bronchial smooth muscle by stimulating β2 receptors.

Now, the question is about an adverse effect. Common side effects of β2 agonists include tremors, tachycardia, palpitations, and hypokalemia. These occur because β2 agonists can also stimulate β1 receptors in the heart, leading to increased heart rate and contractility. Hypokalemia is due to the movement of potassium into cells, mediated by the activation of the Na+/K+ ATPase pump.

The core concept here is the mechanism of action and side effects related to β2 receptor stimulation. The correct answer should be one of these known adverse effects. Let's say the options are A: Tremors, B: Hyperkalemia, C: Bradycardia, D: Constipation.

The correct answer would be A: Tremors. Let me break down why. Tremors are a common side effect because β2 agonists can stimulate β2 receptors in skeletal muscles, leading to muscle tremors. Also, they can cross the blood-brain barrier in some cases, though they're more selective for β2 receptors.

Looking at the wrong options: Hyperkalemia is incorrect because β2 agonists cause hypokalemia. Bradycardia is wrong because they cause tachycardia via β1 stimulation. Constipation is not a typical side effect; in fact, they might cause diarrhea in some cases, but that's less common.

The clinical pearl here is that β2 agonists can have systemic effects, so patients might experience more than just respiratory benefits. Remembering the adverse effects is crucial for managing patients, especially with long-term use. Also, the mnemonic "Tremors, Tachycardia, Hypokalemia" could help students remember the main points.

I need to structure this into the required sections. Make sure each section is concise and hits the key points without being too wordy. Check the character count to stay within the limit. Also, ensure that the explanation is accurate and uses correct medical terminology. Avoid any markdown formatting as per the instructions. Let me put it all together now.

**Core Concept**
β2 agonists like albuterol and salbutamol stimulate β2-adrenergic receptors to relax bronchial smooth muscle, but their adverse effects arise from systemic β1 and β2 receptor activation. Key side effects include tremors, tachycardia, and hypokalemia due to receptor-mediated metabolic and cardiovascular actions.

**Why the Correct Answer is Right**
**Option C:** Tremors are a classic adverse effect of β2 agonists. These drugs activate β2 receptors in skeletal muscles, causing involuntary contractions. Additionally, central nervous system stimulation (via blood-brain barrier permeation in short-acting agents) may contribute to tremors. The mechanism involves increased cyclic AMP (cAMP) and calcium influx, leading to muscle hyperexcitability.

**Why Each Wrong Option is Incorrect**
**Option A:** Hyper

✓ Correct Answer: D. Hypokalemia