Fertilization usually occurs in the. a. fallopian tubes.. b. ovaries.. c. uterus.. d. vagina.

A. Fallopian Tubes

Explanation:

In order to answer the question, we need to review the structure of female reproductive system.

Ovaries are the female gonads (sex organs). They are responsible for the production of egg (ovum).

Fallopian tubes carry the egg from the ovaries to the uterus. It is the fallopian tube where fertilization mostly occurs.

Uterus is a hollow muscular organ. It is responsible for the nourishment of fertilized egg and the subsequent fetus. Fertilized egg is implanted in the uterus.

Vagina is a elastic female reproductive organ it leads from the cervix (lower part of uterus) to the vulva (outer/external female sex organs). It is the birth canal.

Coming back to the question,

A. Fallopian tubes

is the correct answer as fertilization mostly occurs here and the fertilized egg is then carried to the uterus for implantation.

the cell theory states that all living things including animals, as well as plants, are made of cells.

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.