What types of materials are known to reflect RADAR beams?

The correct answer is associated with materials that have properties conducive to reflecting radar waves effectively. Metal, concrete, and stone are known for their dense and solid structures, which enable them to effectively interact with radar signals. Metals, in particular, are excellent reflectors due to their high conductivity, allowing radar beams to bounce off them with minimal absorption. Concrete and stone, while not as reflective as metal, still have sufficient density and surface roughness to scatter radar waves effectively.

Wood and glass may reflect some radar waves, but they are typically not as effective as the materials in the correct answer. Plastic and rubber are generally less effective at reflecting radar because they are less dense and may absorb more radar energy. Water and air do not reflect radar beams effectively; rather, water can absorb radar energy, especially when dealing with certain frequencies, and air does not provide substantial reflective surfaces for radar.