The correct answer is: segmentation.
Segmentation is the fact that some animals and plants have parts of the body that are divided into segments, which typically have a similar structure (they are then called repetitive segments).
Humans also have a segmentation, for example in their spine.
The more feasible reaction is:
2Mg + O₂ → 2MgO
This is because the bond between hydrogen and fluorine is very strong so it does not dissociate easily.
Answer:
It is called pen and it is located at the dorsal side
Explanation:
Squid belongs to the class Cephalopoda, subclass Coleoidea which is characterized by internal shell (unlike subclass Nautiloidea in which shell is located externally).
The shell of the squid (the pen) in very reduced and small, formed from chitin and located at the dorsal side. The pen provides attachment for muscles and it gives the squid stiffness.
Most likely, this internal shell evolved from the external shell, because it is believed the ancestral of the organisms from the Coleoidea was probably nautiloid-like.
