Answer:
;
Explanation:
If In two triangles,
Two pairs of sides of two triangles are in same ratio and there are congruent angle between them,
Then By SAS similarity postulate the triangles are similar.
Here In triangles RST and UVW, (According to the given figure)

And,

Thus,

Also,

Thus, by SAS similarity postulate,

Also, the scale factor or common ratio is

Thus, First Option is correct.