Sentence:  There are three possibilities : ( a ) **f remains <WSD>tangent</WSD> to C as it is translated ; ( b ) **f moves away from C and does not intersect it at all for **f ; ( c ) **f cuts across C and there are two ordinary intersections for every t in **f . 
Meaning of the word marked with <WSD> tags:  a straight line or plane that touches a curve or curved surface at a point but does not intersect it at that point