Answer:-
Ca-Cl
Explanation:-
The more the difference in electronegativity more the polar bond.
In case of Ca-Cl the difference = 3.16 - 1= 2.16
It is more than all the other combinations given.
Hence Ca-Cl is the most polar covalent bond.
Answer:80%
Explanation:Total C in terrestrial ecosystems is approximately 3170 gigatons (GT; 1 GT = 1 petagram = 1 billion metric tons). Of this amount, nearly 80% (2500 GT) is found in soil (Lal 2008).