Could be the sun but that's just me
Answer:
Option c (No, T cells left from the previous infection can kill any virus.
)
Explanation:
When ever viral infection occur, body's immune system start to fight against it by activating B-cells and T-cells.
B-cells produce antibodies that bind with virus and act as label. This label indicate virus as foreign substance. Hence T-cells recognize it and kill it. Furthermore, B-cells form memory cell that keep the viral memory. if this viral infection occur again in future, T-cell recognize it and eliminate the virus.This mechanism is called immunity.
Answer:
The Miller-Urey experiment was conducted to simulate the conditions on Earth when life arose, and see if a chemical evolution could occur. This experiment was performed without oxygen, because they knew that if oxygen was added, the amino acids would oxidize. In particular, the experiment intended to simulate a volcanic eruption was analyzed.
Thus, particles of water, methane, ammonia and hydrogen were exposed to high temperatures and electric discharges that simulated these eruptions, during a determined period. Later, it was observed that organic compounds had emerged from this exposure, which allowed us to infer one of the hypotheses regarding the origin of life on Earth.
The bark of a tree is impervious to gases and water because bark cells are dead cells of the epidermis and compactly arranged without intercellular spaces. They contain a chemical called suberin in their walls that make them impervious to gases and water and it doesn't allow gases or water into the tree as bark cells are in the bark outer most layer of the tree.
