The correct answer is B. 7.95.
The triangle is labeled RST.
U is the midpoint of RS, V is the midpoint of ST, and W is the midpoint of TR.
The side lengths are labeled as follows: RS = 12, ST = 11, and TR = 15.9.
Based on the midpoint information and the given side lengths, the length of UV is 11.
Since U is the midpoint of RS, we know that RU = US = 12/2 = 6.
Similarly, since V is the midpoint of ST, we know that SV = VT = 11/2 = 5.5.
Now, consider the segment UV. It lies entirely within triangle RST, connecting the midpoints of RS and ST.
Therefore, UV is a midline of triangle RST.
A key property of midlines is that they are parallel to the third side of the triangle and half its length.
In this case, UV is parallel to TR and has a length equal to half the length of TR.
Since TR = 15.9, half its length is 15.9/2 = 7.95.
Therefore, the length of UV is 7.95.