If the base pairs in a DNA strand were held together with covalent bonds instead of hydrogen bonds, how would cells have to operate differently? New DNA would need to be made each time the strand was opened.
The cell would have to take in and use more energy in order to break the covalent bonds.
Each time the DNA strand opened the cell would need to replace the nitrogenous bases.
The cell could only open and close the DNA strand when it replicated.

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 !

high growth (apex)

i think its both a and b