Which among the following is classified as a terrestrial planet?

Mars is classified as a terrestrial planet because it possesses a solid, rocky surface, which is a defining characteristic of terrestrial planets. These planets are primarily composed of rock and metal, with a substantial crust and a more ordered geological structure. Terrestrial planets, including Mercury, Venus, Earth, and Mars, have surface features such as mountains, craters, and valleys, which can be studied in detail.

In contrast, the other planets listed are gas giants or ice giants. Jupiter and Saturn are primarily composed of hydrogen and helium, lacking a solid surface, which means they do not fall into the terrestrial category. Similarly, Neptune, an ice giant, is mainly composed of water, ammonia, and methane ices, along with gas, rather than rock. Thus, Mars stands out among the options as the only terrestrial planet.