What do scalars measure

force

acceleration

magnitude

velocity

magnitude.

scalars are units that has magnitude only

vectors have both magnitude and direction

The answer is C, the magnitude.

Explanation:

Because force, acceleration and speed are all vector quantities. That is, to represent them not only reaches a number, but it takes an address, meaning, etc.

Instead a scalar magnitude (for example: temperature, mass) requiere for representation of a single value.