Answer:
d) alternating sugars and phosphates.
Explanation:
DNA is a molecule which acts as the genetic material of the organisms on Earth. The DNA is made of the monomer units called nucleotides which are composed of a sugar called deoxyribose, a phosphate group and two types of nitrogenous bases (purines and pyrimidines).
The DNA structure is known as the double-helical model which gives a ladder-like appearance in a twisted manner. The backbone of the ladder or DNA is made of the deoxyribose sugar and the phosphate group whereas the nitrogenous bases are arranged inside the DNA.
Thus, option-D is the correct answer.