The most commonly used beam in residential construction is:

The most commonly used beam in residential construction is the I-beam, often referred to as an engineered beam due to its efficiency and structural strength. An I-beam is shaped like the capital letter "I," providing high strength while minimizing weight. Its design effectively distributes loads, making it ideal for spanning longer distances without the need for additional support, which is often necessary with solid wood beams.

I-beams are also more resource-efficient because they use less material while maintaining the necessary strength for many residential applications, such as in the floor systems or as headers over large openings. Their popularity stems from their ability to handle greater loads and reduce deflection, which can lead to a more stable structure.

On the other hand, the other options like the 4" x 12" wood beam and L-beams have specific applications that are not as versatile as I-beams in terms of load-bearing capacity over longer spans. Jim Beam, being a brand of bourbon, holds no relevance in construction terminology. Thus, in the context of commonly used materials in residential building, the I-beam stands out for its advantages in both design and performance.