Answer:
Plants are extremely important in the lives of people throughout the world. People depend upon plants to satisfy such basic human needs as food, clothing, shelter, and health care. These needs are growing rapidly because of a growing world population, increasing incomes, and urbanization .
Plants provide food directly, of course, and also feed livestock that is then consumed itself. In addition, plants provide the raw materials for many types of pharmaceuticals, as well as tobacco, coffee, alcohol, and other drugs. The fiber industry depends heavily on the products of cotton, and the lumber products industry relies on wood from a wide variety of trees (wood fuel is used primarily in rural areas). Approximately 2.5 billion people in the world still rely on subsistence farming to satisfy their basic needs, while the rest are tied into increasingly complex production and distribution systems to provide food, fiber, fuel, and other plant-derived commodities .
Medicinal plants have been used in healthcare since time immemorial. Studies have been carried out globally to verify their efficacy and some of the findings have led to the production of plant-based medicines. The global market value of medicinal plant products exceeds $100 billion per annum. This paper discusses the role, contributions and usefulness of medicinal plants in tackling the diseases of public health importance, with particular emphasis on the current strategic approaches to disease prevention. A comparison is drawn between the ‘whole population’ and ‘high-risk’ strategies. The usefulness of the common-factor approach as a method of engaging other health promoters in propagating the ideals of medicinal plants is highlighted.
<h3>ANSWER:</h3>
In case of plants there is a process called PHOTOSYNTHESIS occurs. A photosynthesis is a process in which the carbon and water involves and as a result oxygen plus glucose forms. And because of that plants cause the atmospheric Carbon dioxide decreases as they use the carbon dioxide in the atmosphere.
The correct answer is letter A
Answer: independent variable
Explanation:
Fuel cells can make an electricity from a simple electrochemical
reaction in which oxygen and hydrogen combine to form water. There are several
different types of fuel cell but they are all based around a central design
which consists of two electrodes, a negative anode and a positive cathode.
These are separated by a solid or liquid electrolyte that carries electrically
charged particles between the two electrodes. A catalyst, such as platinum, is
often used to speed up the reactions at the electrodes. Fuel cells are
classified according to the nature of the electrolyte. Every type needs
particular materials and fuels and is suitable for any applications. The
article below uses the proton exchange membrane fuel cell to illustrate the
science and technology behind the fuel cell concept but the characteristics and
applications of the other main designs are also discussed. Proton Exchange Membrane Fuel Cells (PEMFC)
The hydrogen ions permeate across the electrolyte to the
cathode, while the electrons flow through an external circuit and provide
power. Oxygen, in the form of air, is supplied to the cathode and this combines
with the electrons and the hydrogen ions to produce water. These reactions at
the electrodes are as follows:
Anode: 2H24H+ + 4e-
Cathode: O2 + 4H+ + 4e- 2H2O
Overall: 2H2 + O22H2O + energy
PEM cells operate at a temperature of around 80°C. At this
low temperature the electrochemical reactions would normally occur very slowly
so they are catalysed by a thin layer of platinum on each electrode.
