Final answer:
Venus is the most geologically active planet among the terrestrial planets, with ongoing volcanic and geological processes and a molten interior. Mars is less active, while the Moon and Mercury are both geologically dead worlds.
Step-by-step explanation:
Among the terrestrial planets in our solar system, Venus is the most geologically active. The size of a planet is a significant factor in its geological activity, with larger planets generally displaying more activity due to their ability to retain internal heat. Venus and Earth, being the largest terrestrial planets, have continued geological activity with molten interiors. However, Earth exhibits plate tectonics whereas Venus does not but shows other forms of volcanic and geological activity such as coronae and pancake volcanoes. Mars is less geologically active than Venus and Earth, yet it is more active than Mercury and the Moon. The Moon and Mercury are considered geologically dead, having ceased most of their volcanic activity billions of years ago.
Venus and Earth are the most active geologically among the given options. Earth experiences global plate tectonics driven by convection in its mantle, leading to continuous reworking of its surface. Venus, on the other hand, shows levels of volcanic activity similar to Earth but does not have plate tectonics.