The correct answer is option 4: "absorbs and transmits sound."

When sound waves encounter a concrete wall, they can be absorbed and transmitted to varying degrees. This means that the wall can both partially absorb the sound energy and allow some of the sound waves to pass through it. The extent to which a concrete wall absorbs or transmits sound depends on its thickness, density, and surface texture.

Concrete, being a dense and rigid material, tends to reflect sound to some degree, but it is not the primary behavior of a concrete wall. Rather than reflecting sound, it absorbs some of the sound energy and allows the rest to pass through. The absorption and transmission of sound by a concrete wall can be influenced by factors such as the presence of air gaps, cracks, or openings in the wall.

It is important to note that while concrete has some sound absorption and transmission properties, it is not as effective at absorbing sound as specialized acoustic materials. To achieve better sound absorption and reduction, additional soundproofing treatments or materials may be necessary.