During the development of human offspring, which of the following begins to hear and see?
a. fetus
b. embryo
c. blastocyst
d. zygote

Correct A). Fetus

A fetus is a prenatal stage between the embryonic stage and birth. In the human it starts after a ninth week of fertilization and goes until birth.

The eyes of the fetus open first in the 26 to 28 weeks and ear. The baby in the uterus begins to hear after 18 weeks of pregnancy.  

Rest all zygote is formed after fertilization, and after two weeks of fertilization zygote turns in to an embryo.

So, the correct answer would be Fetus.