Answer:
A
B that is Cr,MN,Fe,Co. is the correct answer
C
D
The answer is c.
Elements on the left side of the table are metals, such as sodium, lithium, potassium, etc.
Elements on the right side are non metals, such as Chlorine, Fluorine, Bromine, etc.
Sodium Flouride
Magnesium Nitrate
Calcium Phosphate
Sodium Oxide
Lead Iodide
Copper Sulphate
I've answered another one of your questions with the content of how to work these out
Occurs at a specific temperature