**Core Concept**
Beta-2 agonists are a class of medications that stimulate the beta-2 adrenergic receptors in the lungs, causing bronchodilation and relieving bronchospasm in conditions like asthma. This results in increased cAMP levels, leading to smooth muscle relaxation and decreased airway resistance.

**Why the Correct Answer is Right**
Beta-2 agonists can cause various systemic effects due to their action on beta-adrenergic receptors in other tissues. These include tremors, palpitations, and increased heart rate, as well as hypokalemia due to potassium efflux from cells. Additionally, beta-2 agonists can cause increased glucose release from the liver, leading to hyperglycemia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the systemic effects of beta-2 agonists. While bronchodilation is a desired effect of beta-2 agonists, it's not among the systemic effects listed.
**Option B:** This option is incorrect as beta-2 agonists can cause hyperglycemia by increasing glucose release from the liver.
**Option C:** This option is incorrect as beta-2 agonists can cause hypokalemia due to potassium efflux from cells.

**Clinical Pearl / High-Yield Fact**
Beta-2 agonists should be used with caution in patients with pre-existing cardiovascular disease or diabetes, as they can exacerbate these conditions.

**Correct Answer: A.**