Microscopic plants called algae grow inside the top layer of sea ice in the Antarctic if enough sunlight reaches that layer of i
ce and enough seawater, which contains nutrients, reaches that layer after splashing onto the surface. Even though moderate snow cover reduces the sunlight that filters into the top layer, sea ice with moderate snow cover typically contains even more algae in the top layer than does sea ice with less snow cover. Which of the following , if true most helps to explain the apparent discrepancy?
(A) As the weight of accumulated snow forces ice lower in the water, more seawater splashes onto the surface and seeps through the snow.
(B) Seawater in the Antarctic often contains higher concentrations of nutrients than does seawater in more temperate regions.
(C) As the air temperature around sea ice decreases during the winter, the likelihood decreases that snow will fall and thus add to any existing snow cover.
(D) The nutrients on which algae rely are common in seawater throughout the Antarctic.
(E) More sunlight filters through a layer of ice than through an equally thick layer of snow.
In the question, it is mentioned that the algae can grow under the conditions of "enough sunlight" and "enough nutrients".
Sunlight reaches the algae, by first falling on the surface made up of ice and snow and then refracting from there into the top layer of the ice where the algae grows.
However, the capability of both snow and ice to reflect sunlight is far more than that of refracting sunlight.
Therefore, the amount of light received by the algae is similar in absence or presence of the layer of snow on the top layer of ice.
However, on deposition of snow on the layer of the ice, the weight of the ice increases and it sinks below into sea water.
This allows more nutrient rich sea water to percolate into the ice and reach the algae.
The algae receive more nutrients from the sea water and hence is capable undergoing better metabolism and growth.
Hence, more algae are produced under such a situation.
The purpose of the fine focus knob is to sharpen the focus quality of the image after it has been brought into focus with the coarse focus knob. Illuminator, There is an illuminator built into the base of most microscopes.
