Answer: B
Explanation:
The T helper cell needs to acttivate the T cyctotoxic cell in order for the Tc cell to go do its work.
Once the TC cell is active it interacts with MHC-1 proteins on the surface of the infected host cell, this allows the Tc cell to recignise the host cell and begin secreting cytotoxins (perforins and granzymes) in order to degrade the infected cell and cause apoptosis (controlled cell death)
the largest planet in our solar system is Jupiter
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Answer:
Density is nearly 3 cabs per hectare
Explanation:
Given -
There are three three intertidal regions.
Area of each intertidal region is 
hectares.
Number of crab in the intertidal regions are as follows -
Intertidal region I - 7
Intertidal region I - 2
Intertidal region I - 6
Sum of crabs in all three regions is equal to
Total area of all three intertidal regions is equal to
hectares
Now density per hectare is equal to total population of crab divided by total area of all the three intertidal regions
Density 
Density is nearly 3 cabs per hectare
Answer:
The snakes keep the mice from overpopulating, which could deplete their resources.
Explanation:
The mice and the moles are not competing against each other as they feed on different food. The problem is that if the mice population is not regulated, their very quick reproduction will cause overpopulation in very short space of time. The more mice there will be , the more food will be needed, so very soon the resources will be depleted, resulting in collapse of the mice population. This is where the snakes come in action, as they eat mice, so they are the ones that control and keep their population stable, thus not allowing the mice to overpopulate the area and destroy themselves.
