What is the backbone of dna made of?
sugar and phosphates
nitrogenous bases and sugar
nitrogenous bases, sugar, and phosphates
a polymer of nitrogenous bases

The correct option is sugar and phosphates.

Explanation:

The DNA molecule consists of two strands (filaments) that are rolled over each other to form a structure known as a double helix. Each filament has a "backbone" made of alternating sugars (deoxyribose) with phosphate groups, that is, the primary structure of the DNA is determined by the sequence of bases (adenine, thymine, cytosine and guanine) arranged on the "column" formed by the nucleosides: sugar and phosphate. Phosphate backbone is the portion of the double helix of DNA that provides structural support to the molecule.

d concave shape of wave rock

explanation:

the concave shape of wave rock is a very good evidence that supports the evolution of earth due to chemical weathering. if we talk about structure of   wave rock, studies have estimated that it is around 2.7 billion years old. it also serves as the foundation of evidence that it was the place where australian continent began to form.

how the structure of wave rock was created?

studies suggest that structure of wave rock was created when the surrounded area was started to weather due to which deposition of material started on the part of land which now contains wave rock.

the structure of wave rock is considered to be one of the best-known landforms in australia. at the height of around 15 cm, there can be found flared slopes which formulate the margins of hyden rock. it is now assumed by geologists that wave rock was created by subsurface water-induced weathering and not by glaciers, waves or wind.

due to deposition of material over the period of long time, the wave rock became tougher and tougher due to weathering from surrounding terrain. this makes it a physical evidence that supports   the evolution of earth due to chemical weathering.

hope it !