Amongst the following the most basic compound is

Which one of the following methods is neither meant for the synthesis nor for separation of amines?

An organic compound having molecular mass 60 is found to contain C = 20%, H = 6.67% and N = 46.67% while rest is oxygen. On heating it gives NH₃ along with a solid residue. The solid residue give violet colour with alkaline copper sulphate solution. The compound is

In both DNA and RNA, heterocyclic base and phosphate ester linkages are at-