Answer:
It is none. Echo is formed when sound waves hit a hard surface.
Explanation:
The independent variable belongs on the x-axis (horizontal line) of the graph and the dependent variable belongs on the y-axis (vertical line).
Answer:

Explanation:
For a charged particle accelerated by an electric field, the kinetic energy gained by the particle is equal to the decrease in electric potential energy of the particle; therefore:

where
is the final kinetic energy
is the initial kinetic energy
q is the charge of the particle
is the potential difference
In this problem,
is the charge of the electron

The electron starts from rest, so its initial kinetic energy is

Therefore,

We can write the final kinetic energy of the electron as

where
is the electron mass
v is the final speed
And solving for v,

The answer would be, "Electrons".