I'm pretty sure the answer is B
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.
Leaves in areas of low humidity have a steeper concentration gradient so water diffuses out of the leaf fast.
<h3>What is humidity?</h3>
Humidity is used to determine the concentration of water vapour that is available in the air.
when the vapour is high there is high relative humidity when the vapour is low there is low relative humidity and water leaves the surface of leaf fast.
Therefore, Leaves in areas of low humidity have a steeper concentration gradient so water diffuses out of the leaf fast.
Learn more on humidity here,
brainly.com/question/5362026
<span>Myelitis is the inflammation of the spinal cord it also means inflammation of bone marrow. Transverse myelitis is an inflammation of both sides of one section of the spinal cord. This neurological disorder often damages the insulating material covering nerve cell fibers. Transverse myelitis interrupts the messages that the spinal cord nerves send throughout the body.</span>
Answer: Several types of evidence supported Hess's theory of sea-floor spreading: eruptions of molten material, magnetic stripes in the rock of the ocean floor, and the ages of the rocks themselves. This evidence led scientists to look again at Wegener's hypothesis of continental drift.
Explanation:
