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.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.