1) C. velocity
Acceleration is defined as the rate of change of velocity per unit time. In formulas:

where
is the change in velocity
is the time interval
Therefore, the correct answer is C. velocity.
2) A. 9.8m/s/s
Earth's gravity is a force, so it produces an acceleration on every object with mass located on the Earth's surface. This acceleration can be calculated, as it is given by the formula

where
is the gravitational constant
is the Earth's mass
is the Earth's radius
By substituting these numbers into the formula, one can find that the acceleration due to Earth's gravity is
.
There is kinetic energy when it is sitting at the top, then as it goes towards the bottom, the kinetic energy is transformed into potential energy.
To find the average of data collected, add all of the measurements: 5.9+6.2+6.3+6= 12.2
Then, divide the total amount by the number of data collected which is 4: 12.2/4= 3.05
The average speed of the runner of the race is approximately 3.05 km/min
Feel free to ask me any other questions you might have :)
Technician A and B are correct . Because according to technician A, the cause written on the repair order is a diagnosis. Here, by diagnosis, he means that the problem is identified after examining the device and hence the judgement is made.
And according to B, you have to write the cause of the problems in the device that have been identified and the concern measures, which is also kind of diagnosis.
So, option D is correct.