Answer:
4.6
Explanation:
W is the mid point of ST
U is the mid point of SR
V is the mid point of TR
Mid point theorem : It states that the segment joining two sides of a triangle at the midpoints of those sides is parallel to the third side and is half the length of the third side.
So By theorem,

WU = 1.7
So,



Since V is the midpoint of RT
So,


Basic Proportionality Theorem : It states that, if a line is parallel to a side of a triangle which intersects the other sides into two distinct points, then the line divides those sides in proportion.
So, Using theorem :

So,



Thus the length of SR is 4.6
Hence Option D is true.