Answer: option c. magnitude and direction
Explanation:
1) Force is a vector: it has magnitude and direction.
2) Magnitude measures the "intensity" of the force. It is measured in newtons (N), in the SI (international system of units). One newton is the force exerted to confere an acceleration of 1 m/s² to a mass of 1 kg.
3) Telling the magnitude of the force is not enough information to understand what the force is and to predict its effect.
It is necessary to tell the direction in which the force is applied.
It is not the same a force of 10 N that pulls that the same magnitude pushing. And it is not the same a hhorizontal force of 100 N to move an object, than the same magnitude applied at an agle.
That is why the force must be measured and reported as a magnitude and a direction.
4) Examples of forces correctly reported are:
i) 100 N vertically upward
ii) 1000 N 20° to the east of the north.
iii) 0.2 N with an elevation angle of 50°.
Then, scientists must measure the magnitude and the direction of the force.