Answer:The bases used in DNA are adenine (A), cytosine (C),
I only had time to answer one srryyy
Answer:
Air speed of bird is
mph
Explanation:
let the speed of the bird in still air be "X"
Speed of the bird when it flies in the direction of flow of wind 
Speed of the bird when it flies in the opposite direction of flow of wind 
The total time taken is equal to
minutes
hours
The distance in miles is equal to
miles

On solving the above equation, we get -

Air speed of bird is
mph
Answer:
The culture of a civilization can be changed by the biological situations that surround a society.
Explanation:
Foe example, in eating habits, if there is a society that leave in a place where there is going to grow plenty of fruits and vegetables like in the Caribbean places, people will be used to eat bananas. At the same time fashion or design behaviors or tendencies will be full of color because is the environment that surrounds the artist. At the same time, some language expressions will be formed by comparing animals of fruits of the environment with comparison in the society for example: "cuando suena el rio es porque lleva piedras" (when the river sounds is because it has some rocks) of course this idea means that when is a rumor, is because there is an explanation for it. But of course the relationship is because people can observe how is the normal behavior of a river.
Hope this info is useful.
Viruses need a host because a host is just like the owner of the virus "business". think of it as a company. the company has a boss- aka the person who made the company (this is the host) and the boss also tells the employees (bacteria etc) what to do and how to do it. without the host, the virus will die. :)