The term $Annulus$ is derived from which language?

What is the phenomenon called where the body of some animals is externally and internally divided into segments with a serial repetition of at least some organs?

Which type of metamerism is observed in earthworms?

Haemoglobin is dissolved in the blood plasma of:

Larval stages are absent in the life cycle of . . . . . . .

$A$: Annelids exhibit extracellular digestion.
$R$: The digestive tract in annelids is complete.