DNA is made up of (nucleotides / nitrogenous bases), joined by covalent bonds between the (adenine / guanine / thymine/ deoxyribose) of one monomer and the (phosphate group / nitrogenous base) of the next monomer. The DNA of all members of a species has (the same / a different) nitrogenous base composition. The percentage of (adenine (A) / guanine (G) / thymine (T) / cytosine (C)) always equals the percentage of thymine (T), and the percentage of (adenine (A) / guanine (G) / thymine (T) / cytosine (C)) equals the percentage of cytosine (C). It follows that if the percentage of adenine plus thymine equals 40%, then the percentage of guanine plus cytosine would equal (15% / 20% / 30% / 60%)​