In which of the following phyla did a true coelom first evolve?

$A$: The first circulatory system is observed in the phylum Annelida.
$R$: The first true coelom is observed in the phylum Annelida.

Animals with metameric segmentation, bilateral symmetry, and a closed circulatory system belong to which phylum?

$A$ student was given a specimen to identify on the basis of the characteristics given below.
$(i)$ They are metamerically segmented.
$(ii)$ Presence of closed circulatory system.
$(iii)$ They have circular and longitudinal muscles for locomotion.
Identify the specimen.

In the evolution of animals,a heart to pump the blood is found for the first time in

Which one of the following is not a hermaphrodite animal?