6. the combination of all of the forces acting on
an object?

The combination of all the forces acting on an object is the net force. Forces may work together or they may be opposite forces. Two or more opposite forces are balanced forces if their effects cancel each other and they do not cause a change in an object's motion.

Explanation:

materials water oxygen those are the things i can think of in this moment.

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.