Final answer:
Earth is the only known planet with life, uniquely suited due to its distance from the Sun, atmosphere, and presence of water, standing out as habitable in contrast to Venus and Mars.
Step-by-step explanation:
The planet between Venus and Mars is Earth, which is indeed the only planet where life has been found so far. It is true that Earth has the right conditions that have allowed life to thrive for billions of years. Earth's unique qualities, such as its distance from the Sun, the composition of its atmosphere, and the presence of water, have made life possible here.
While there is evidence that Mars may have had habitable conditions in the past, and that there might be habitable environments in the subsurface of Mars or inside the icy moons of the outer solar system, Earth remains the only known planet with life. Due to the lack of evidence for life and the very different environmental conditions on Venus and Mars, Earth stands out as uniquely habitable in our solar system.