The correct answer is option 1 - Mercury. Terrestrial planets are a type of planet that are primarily composed of rock and metal. They are also known as inner planets because they are located closer to the Sun compared to the outer planets.

Option 2 - Jupiter is not a terrestrial planet. Jupiter is a gas giant and is composed mainly of hydrogen and helium gases, with no solid surface.

Option 3 - Saturn is also not a terrestrial planet. It is another gas giant and is similar in composition to Jupiter.

Option 4 - Uranus is also not a terrestrial planet. Uranus is an ice giant and is composed mostly of ices such as water, ammonia, and methane.

It is important to note that the distinction between terrestrial planets and gas giants is based on their composition and location in the solar system. Terrestrial planets have a solid surface and are closer to the Sun, while gas giants are mostly made up of gases and are located farther away from the Sun.