The mesencephalon gives rise to the midbrain and aqueduct of
the midbrian(cerebal aqueduct). Both the prosencephalon and rhombencephalon
develops in to the metencephalon and myelencephalon. The telencephalon develops into the cerebrum
and lateral ventricles. The diencephalon forms the thalamus, hypothalamus, and
epithalamus.
C. They are not enclosed by a membrane.
D is incorrect because Ribosomes do not contain DNA, the nucleolus does.
B is also incorrect because they aren't located outside the cell, they're in the cell, on the endoplasmic reticulum.
Hoped this helped :)
I believe the answer to your question is isokinetic, isometric, and isotonic
Adaptation through natural selection
Answer : A metal in group 16 of the periodic table can become a chemically stable ion by gaining 2 electrons.
Explanation :
The group 16 element are oxygen, sulfur, selenium, tellurium and polonium.
The general electronic configuration of group 16 elements is, 
As we now that there are total 6 electrons in p sub-shell. So, a metal in group 16 can become a chemically stable ion by gaining 2 electrons.

Hence, a metal in group 16 of the periodic table can become a chemically stable ion by gaining 2 electrons.