The bond formed between the first phosphate group and adenosine in $ATP$ is

In the given figure,what does $A$ indicate?

Which of the following protects from scurvy?

Match the names of items listed under column $I$ with the items given under column $II$; choose the answer which gives the correct combination of the alphabets of the two columns.

Column $-I$	Column $-II$
$(A)$ Ketone	$(p)$ Has $5$ carbon sugar,a phosphate group and a nitrogenous base
$(B)$ Fatty acid	$(q)$ Has long chain of carbon and hydrogen atoms and a carboxyl group at one end
$(C)$ Aldehyde	$(r)$ Has a carbonyl group at the end of the carbon chain
$(D)$ Nucleotide	$(s)$ Has a carbonyl group within the carbon chain

The energy released by one molecule of $ATP$ is approximately: (in $kcal$)

What do "a" and "b" represent in the given structure of the nitrogenous base?