Human populations in low-uv environments tend to have more lightly pigmented skin. one explanation is that the selective pressure for dark skin decreases as uv intensity decreases. at the same time there is selection for lighter skin to absorb more uv radiation, which is needed for vitamin d production. what evidence supports the vitamin d hypothesis for the evolution of lighter skin tones? a. lightly pigmented people tend to be at higher risk of vitamin d deficiencyb. red hair and light skin are typical of people of northern european descentc. lightly pigmented people cannot synthesize vitamin d in high-uv environments, such as equatorial africa. d. indigenous peoples living at high latitudes have darker skin, but they eat foods rich in vitamin d.

Lightly pigmented people tend to be at higher risk of vitamin D deficiency

Explanation:

BACKGROUND KNOWLEDGE:

Human skin is the largest organ of the body which makes boundary line between environment and internal conditions.  Human skin cell produces pigment called melanin when ever it is subjected to Sun. More the melanin pigment produced more will be the skin darkens. Ultraviolet (UV) radiations also come from Sun and responsible for more pigmentation.

ANSWER EXPLANATION:

According to the question darkly pigmentation only occurs when their is high level of UV radiations. High level of UV radiations are also responsible for Vitamin D production.

People with lightly pigmented means that there environment has low level of UV radiations which are the requirement of Vitamin D production. Hence due to low UV radiations peoples with light pigmentation's are also be at higher risk of vitamin D deficiency

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 !