Answer:
c) Combustion of fossil fuels
Explanation:
Burning of fossil fuels is the main cause of increasing carbondioxide concentration in the environment which results in air pollution. This increase in carbondioxide concentration absorbed more heat energy from reflected solar radiation which increases the temperature of earth surface causes global warming. Due to this global warming, snow melting occurs on the poles of the earth which increases sea level.
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Percentage of human sperm cells carry an X chromosome is C 50%
Helper T cells <span>are required for almost all </span>adaptive immune responses<span>. They not only help activate B </span>cells to<span> secrete antibodies and macrophages </span>to<span> destroy ingested microbes, but they also help activate cytotoxic </span>T cells to<span> kill infected target </span>cells<span>.</span>
Answer:
Muscles can also receive messages from the brain when the body temperature decreases. They respond by shivering. Shivering causes the muscles to contract and relax quickly. This process generates heat.