Answer is: B.)The velocity of a car reduced from 50 km/h over one minute.
Ending velocity is defined as the velocity attained by a body after completing distance at certain time interval:
v(ending velocity) = v(initial velocity) + a·t.
a is acceleration attained by the body (in this examle car).
t is time (in this example one minute).
Because velocity is reduced, acceleration has negative sign.
An car average acceleration over a period of time is its change in velocity.
