Why does the video show many people ducking and covering in a variety of situations? a. to show that duck and cover was not the best way to be safe during an atom bomb attack b. to show that duck and cover could not keep a person safe c. to show that duck and cover would protect a person during an atom bomb attack d. to show what not to do during an atom bomb attack.

C. To show that duck and cover would protect a person during a bomb attack.

That answer doesn't make much sense to us now, but at the time of the 1951 Duck and Cover film released by the US Civil Defense office, that was the message the government was conveying to the American people.

If you look at the other options in the answer choices, all of them (A,B,D) are essentially saying the same thing -- that this was a method that would not work.  So the only unique answer in the set -- which was the message from Civil Defense -- was that "duck and cover" was a helpful strategy in the event of a nuclear attack.  Truthfully, it would not have been.

The constant presence of diseases or infectious agents within a given geographic area or population group. it may also refer to the usual prevalence of a given disease with such area or group. it includes holoendemic and hyperendemic diseases. a holoendemic disease is one for which a high prevalent level of infection begins early in life and affects most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do children (malaria in many communities is a holoendemic disease). a hyperendemic disease is one that is constantly present at a high incidence and/or prevalence rate and affects all groups equally. so probably family history.