Excretory structures known as protonephridia are present in
A) cnidarians.
B) earthworms.
C) vertebrates.
D) insects.
E) flatworms.
Answer: E
Excretory structures known as protonephridia are present in
A) cnidarians.
B) earthworms.
C) vertebrates.
D) insects.
E) flatworms.
Answer: E