An experiment was designed to test the effect of ultraviolet light on the growth of mold spores. A sample of mold spores was divided into two groups. The groups were grown under the same conditions, except that group A was exposed only to ultraviolet light and group B was grown in total darkness. What is the purpose of group B being grown in total darkness? To limit bias

It is the dependent variable

It is the control group

To add an alternative variable

C

Explanation:

answer and explanation;

volcanic rocks are igneous rocks which form from lava, molten rock which has been thrust out of a volcano onto the surface of a rocky body such as an asteroid, planet, or dwarf planet.  

plutonic rocks are igneous rocks which form from subterranean chambers of molten rock or magma. plutonic rocks make up the base of continental crust as well as oceanic crust. their slow rate of formation causes them to be coarse grained since there is plenty of time for large crystals to form before the magma solidifies into rock.

the textural difference is that plutonic rocks are more coarse grained than volcanic rocks. plutonic rocks are coarse grained while volcanic are fine grained ; glassey or fragmental. since fine and coarse are adjectives the decision as to whether a rock is fine or coarse grained is generally made on the bases of whether or not the individual crystals can be seen in most if the rock.