$A$ rod-like structure formed on the dorsal side during embryonic development in some animals, which is mesodermally derived:

Excretion by protonephridia with solenocytes is a characteristic of

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ All vertebrates are chordates but all chordates are not vertebrates.
Reason $(R):$ The members of subphylum Vertebrata possess a notochord during the embryonic period; the notochord is replaced by a cartilaginous or bony vertebral column in adults.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following is another characteristic of animals possessing a solid nerve cord?

The group $Amniota$ includes:

Observe the following simplified scheme of the division $Vertebrata$ and choose the correct option that matches with the letters given in the boxes.