Question

a(n) _ is a one - celled organism formed by the union of a sperm and an egg.
a zygote
b blastocyst
c embryo
d fetus
please select the best answer from the choices provided
○ a
○ b
○ c
○ d

Explanation:

A zygote is formed when a sperm fertilizes an egg. A blastocyst is an early - stage embryo with multiple cells. An embryo is a developing organism (more than one - celled in most cases). A fetus is a more developed stage after the embryonic period. So the one - celled organism from sperm - egg union is a zygote.

Answer:

A. zygote