Answer:
One Dimensional.
Explanation:
A straight line is a basic geometric object studied from the Ancient Greece by the Greek geometers, and likewise that the plane and the space, the straight line is called an Euclidean Space. The concept of dimension is more recent, it is a consequence of the correspondence between real numbers and points in the Euclidean Space. So dimension is related with the numbers of coordinates required to represent the points in a certain Euclidean Space. In the case of the straight line only one coordinate is suffice to represent a point. When we have a straight line with coordinates it is called the Real Line.