What celestial body lies between Mars and Jupiter?

The celestial body that lies between Mars and Jupiter is the Asteroid Belt. This region is populated with numerous rocky fragments and larger bodies that orbit the Sun. These asteroids are remnants from the early solar system, thought to be leftover materials that never coalesced into a planet due to Jupiter's strong gravitational influence. The Asteroid Belt serves as a distinct boundary between the inner, terrestrial planets (like Earth and Mars) and the outer, gaseous planets (like Jupiter and Saturn).

The other options listed represent different structures in the solar system. The Gas Giants refer to the outer planets collectively, which are not located between Mars and Jupiter. The Kuiper Belt is found beyond Neptune and is home to icy bodies, including dwarf planets like Pluto. The Oort Cloud is a theoretical region far beyond the Kuiper Belt, thought to be the source of long-period comets, and does not lie between Mars and Jupiter. The Asteroid Belt is thus the correct answer as it specifically occupies the region between these two planets.