C. Magma from venus mantle erupted as lava.
Explanation:
A volcano is a land form which results from the eruption of molten rocks (lava) on the surface. Volcanic rocks are a special type of igneous rock that forms when molten rock cools and solidifies on the surface.
For a planet like Venus which is presently not active and little to no movement occurs within the plates, the volcanisim must have occurred when the planet was relatively young and it must have been millions of years ago.
It is widely believed that Venus was geologically active in times past. Mantle generated lava must have solidified on the surface in times past to have formed the volcano.
Evaluating other options:
Impact of space objects on Venus would lead to the formation of a crater which is a depression on the surface. The rock would be mostly metamorphic.
If water was ever present in Venus, they would have produced sedimentary rocks instead. The erosive power of water is not high enough to cut through the crust. Also, water would not aid the formation of volcanoes.
Heat is not enough to from volcanoes. Other factors are also in play.
The answer would be KMnO4, please let me know if you would like me to explain how i got this
In chemistry the law of multiple proportions states that if two elements from more than one compound between them then the ratios of the masses of the second element which combine with a fixed mass of the first element will always be ratios of small whole numbers .
These rocks were either roasted or exposed to severe weathering
Approximitly 0.013787375 moles