What components do trunk lines typically consist of in a draft beer system?

In a draft beer system, trunk lines typically comprise both barrier tubing and glycol tubing. Barrier tubing is essential because it helps maintain the quality and integrity of the beer as it travels from the keg to the tap. This type of tubing minimizes oxygen ingress and reduces the chance of off-flavors due to light exposure. Glycol tubing, on the other hand, is important for temperature control. It circulates a chilled glycol solution that cools the beer lines, ensuring that the beer maintains an optimal serving temperature right up to the point of dispensing. This dual approach in trunk line construction is critical for delivering high-quality draft beer consistently and efficiently, making it the correct choice among the options presented.

The other options, while mentioning various types of materials used in beer systems, do not encompass the necessary components of a proper trunk line in a draft beer setup. For instance, stating that it consists solely of beer tubing or vinyl tubing fails to address the need for temperature regulation and quality preservation provided by the combination of barrier and glycol tubing.