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 main reason is that there is no atmosphere. This means that there is no weather and no weather means that there is no wind or rain. Wind and rain are main components of erosion and because there is no erosion, craters can stay preserved for a very long time.
Hope this helps!!
