This question is incomplete. Here is the complete question:
Pumice is a lightweight rock that sometimes forms when lava is very rich in _____. A. silica B. gases C. feldspar D. volcanic glass
Answer:
The correct answer is option D. volcanic glass.
Explanation:
Pumice stone is a very common stone used for construction or cleaning among other things.
This rock is formed through lava that contains water and gas and comes from the inside of a volcano, so when this lava is thrown out of the volcano it cools and hardens, and is filled with bubbles of volcanic gas.
This type of rock is low density and can float on water.
Given this information we can say that the correct answer is the option D. volcanic glass
