Answer:
A) 
B) 
C)
or
hours
Explanation:
A) The formula that can be used for bacteria after "t" hours is

Where ,
represents the population after "t" hours
represents the initial population.
represents the rate of growth of population
represents the time taken by the population to grow
B) Here let us first find the rate of population growth.

Thus, the population of bacteria after 5 hours

C)

Absolute refractory period -
the period immediately following the firing of a nerve fiber when it cannot be stimulated no matter how great a stimulus is administered