What is the only planet smaller than Mars?

Here is the question :

WHAT IS THE ONLY PLANET SMALLER THAN MARS?

Here is the option for the question :

Earth
Venus
Mercury
Uranus

The Answer:

And, the answer for the the question is :

Mercury

Explanation:

[STC003893] Mars is a very small planet, almost half the size of Earth, yet it plays a significant role in our hopes to explore the rest of the solar system. Mercury, which orbits closest to the sun, is the only other planet in the solar system that is smaller than Mars. Mercury is approximately two-thirds the size of Mars.