Final answer:
Between any two distinct points, there will always be one distinct line.
Step-by-step explanation:
The correct answer is a. always. Between any two distinct points, there will always be one distinct line. This statement is valid in different contexts within the field of physics.
For example, in mathematics and geometry, any two distinct points can be connected by a straight line. In physics, electric-field lines and magnetic field lines represent the direction of the field, and they never cross each other.