Answer:

Explanation:
The average speed is defined as:

Using the equations for uniformly accelerated motion, we calculate the runner's acceleration:

Now, we can calculate the distance that the runner travels:

Finally, we calculate the runner's average speed:

Answer:
Water can spread germs through bacteria.
Explanation:
Bacteria can live in water and can spread to new locations when water is moved.
This is called the Doppler Effect. It is the alteration in frequency of a wave when the source, the light waves in this situation, and the observer are moving away from each other. The reason for stars to appear further from the observer is the constant expansion of the universe.