Guanine and cytosine are important constituents of
a. most protein molecules.
b. the chromosome of a cell.
c. all of these.
d. the cellular membrane.
e. most acid solutions

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

c: warm water flows from the western tropical pacific toward south america. that should be the right answer! hope it .