We have two points known to be ( S ) and ( T ). A line connects two points.
The minimum number of points that are required to form a straight line in a cartesian coordinate system are ( two ).
The minimum number of points that are required to form a plane in a cartesian coordinate system are ( three ) which will form two vectors i.e it requires two lines formed with a common point.
Two planes always intersect at exactly one point with direction normal to the two plane normal vectors.
Hence, the only possible postulate that relates two points is the formation of a line between two points; hence, the correct postulate for the given statement is:
