Which of the following features is not a characteristic of $Protochordata$?

$A$ plant specimen was found without differentiated roots.
$(a)$ Which plant structure helps in attaching this plant to the substratum?
$(b)$ To which group would you classify this plant?
$(c)$ Which plant could it be?

Which among the following phyla is exclusively marine?

Amphibians do not have the following:

Sehai and Sidak observed an animal in their garden. Sehai called it an insect while Sidak said it was an earthworm. Choose the character from the following which confirms that it is an insect.

Which among the following have an open circulatory system?
$(i)$ Arthropoda
$(ii)$ Mollusca
$(iii)$ Annelida
$(iv)$ Coelenterata