Temperature regulatory apparatus of the mammal include the following pairs a. epidermis and dermis
b. hair follicles and nerve ends
c. sweat glands and sebaceous glands
d. sweat glands and hair follicles​

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.