The right answer is <span>Refractory period.
At the moment when the action potential is emitted, the fiber being depolarized, it is impossible to depolarize it again. It is, therefore, necessary to wait until the membrane potential returns to a value below the critical threshold in order to be able to excite it again. We are thus led to distinguish two periods that characterize its excitability.
An absolute refractory period: during which any stimulation, even supraliminal, is ineffective since the fiber is already depolarized.
A relative refractory period: during which a second action potential can be omitted provided that the depolarization produced by the excitation reaches the critical threshold, which implies that it is more important since the value of the resting potential has not been restored yet.</span>
(I wrote to you more than three types)
There are seven known types of human coronavirus. Four common types (KHUI, OC43, NL63,229E) cause mild to moderate respiratory infection, such as the common cold. There are two types, severe acute respiratory syndrome (SARS-COV) and Middle East respiratory virus syndrome (MERS-COV), that can cause acute respiratory infections. Type VII (nCOV-2019) is the newly discovered novel coronavirus in China.
Answer:
Because of using fossil fuels nowadays it is used to air pollute the earth causing global warming.
Explanation:
A. Smallpox could make a good biological weapon because it is an airborne virus.
B. Smallpox can be prevented via vaccination and potentially prevented by HEPA filters.
