Which of the following is a vector quantity?

Force is classified as a vector quantity because it has both magnitude and direction. In physics, vectors are quantities that are fully described by both a size (how much) and a direction (where it is going). For instance, if a force is described as "10 newtons to the east," it clearly indicates how strong the force is (the magnitude, 10 newtons) and the direction (to the east).

In contrast, mass and temperature are scalar quantities. They have magnitude but no specific direction associated with them. Mass refers simply to the amount of matter in an object, while temperature indicates the thermal state of an object without any directional component. Speed is also a scalar quantity that tells us how fast an object is moving but does not provide any information about the direction of the movement. Therefore, considering the characteristics of vector quantities, force is the correct answer.