Final answer:
Phenylephrine is a bronchodilator drug that widens the bronchi to treat asthma by opening the airways wider.
Step-by-step explanation:
A bronchodilator drug that widens the bronchi and is commonly used to treat asthma by opening the airways wider is phenylephrine. Phenylephrine is a sympathomimetic drug that binds to adrenergic receptors in the bronchioles of the lungs, causing them to dilate. This helps increase air volume in the lungs and alleviate symptoms of asthma such as difficulty breathing and wheezing. Phenylephrine is often found in decongestants and can be combined with other pharmaceuticals to effectively treat respiratory conditions.