Final answer:
A prehistoric monument of large upright stones supporting a horizontal slab is described as a dolmen, with 'henge' being the closest option given. Stonehenge, the notable structure of this kind, was constructed using the post-and-lintel technique and aligns with celestial bodies.
Step-by-step explanation:
A prehistoric monument consisting of two or more large upright stones supporting a horizontal stone slab is best described as a dolmen. This is not one of the options provided, but if we look at the options given, the closest match would be a henge, although this is not the precise definition of the structure described. This particular description does not accurately define the other options: a stele, which is a tall carved stone; a cairn, which is a mound of stones built as a memorial or landmark; and a menhir, which is a single standing stone often of prehistoric origin.
Stonehenge is a world-famous prehistoric monument that embodies these characteristics, comprised of a series of such structures called trilithons. Construction of Stonehenge began around 3100 BCE as an earthwork henge and evolved over hundreds of years. The neolithic builders utilized a post-and-lintel technique, quarrying, transporting, and erecting massive stones to create a complex that has both religious and astronomical significance, tracking the motions of the Sun and Moon.