Thymine and cytosine differ from adenine and guanine in that

The correct answer is: thymine and cytosine are single-ring structures called pyrimidines.

Explanation:

Thymine, Cytosine, Adenine and Guanine are the nitrogenous bases that form the four nucleotides in DNA strands. In RNA strands, there's no thymine but there's uracil.

These bases have the function to be the fundamental units of the genetic code.

The structure of these nitrogenous bases consists of a skeleton with the shape of one ring (which grants them the name of pyrimidines) or two fused rings (these are called purines). Thymine and Cytosine are pyrimidines, while Adenine and Guanine are purines.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

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.