Option C:
We can find the value of PR using law of cosines.
Solution:
Given data:
∠Q = 18°, r = 9.5, p = 6.0
To find which length could be find in the triangle:
Law of cosines:

Substitute a = q, b = r, c = p and A = Q

If we substitute the values given, we can find q.
q = PR

Hence we can find the value of PR using law of cosines.
Option C is the correct answer.