Option D
polymerase chain reaction (PCR) do Makes more copies of a sample of DNA
<u>Explanation:</u>
A procedure to create several portraits of a distinct DNA section is termed as Polymerase chain reaction. In other words, it is a lab routine handled to compose various representations of a portion of DNA. PCR is extremely explicit and can be utilized to increase, or model, a particular DNA destination from a hybrid of DNA particles.
In PCR, the effect is regularly cycled within a range of temperature variations, which deduct countless models of the destination range to be exhibited. PCR intends to obtain sufficient of the objective DNA region that it can be examined or applied in some other way.
The answer is; the melanin in darkly pigmented skin protects DNA from UV radiation, and UV radiation can cause skin cancer
In Africa, due to its equatorial latitude location, receives direct sunlight at more or less 90 degrees most of the year. These highly concentrated rays increase the UV radiation exposure that can cause damage to cell DNA. Selection pressure, therefore, favored individuals with high melanin concentrations that protect against UV. Therefore population evolved towards high melanin densities in the skin.
The best answer is B
Deltas are wet lands that form as rivers empty their water and sediments into another body of water such as an ocean, lake, or another river. Deltas can also empty into land although this is less common.
A river moves more slowly as it nears its end. This causes sediment, solid material that has been carried downstream by the water to fall to the river bottom.
The slowing of the river and the build up of sediment allows the river to break up from its single channel to several channels forming a triangular flow at the mouth called a delta.
