In $Pheretima$,oxygen-carrying haemoglobin occurs in:

Integumentary nephridia are also called

Which of the following statements is true regarding haemoglobin?

$Pheretima$ is:

Pharyngeal nephridia in $Pheretima$ are found in segments:

Following are the statements about the prostomium of an earthworm.
$(a)$ It serves as a covering for the mouth.
$(b)$ It helps to open cracks in the soil into which it can crawl.
$(c)$ It is one of the sensory structures.
$(d)$ It is the first body segment.
Choose the correct answer from the options given below.