Which one of the following organisms bears hollow and pneumatic long bones?

Bilaterally symmetrical and acoelomate animals are exemplified by

Which of the following statements are true for the phylum-Chordata

(i) In Urochordata notochord extends from head to tail and it is present throughout their life.
(ii) In Vertebrata notochord is present during the embryonic period only.
(iii) Central nervous system is dorsal and hollow.
(iv) Chordata is divided into 3 subphyla: Hemichordata, Tunicata and Cephalochordata.

If the head of cockroach is removed, it may live for few days because