**Concept: The question tests on the basics of Counting**

**Solution:**

Probability = Favorable Outcomes / Total Outcomes

PRINCIPLE has 9 letters 2 P's, 2 I's, and 1 each of R,N,CL and E

Total Outcomes = 9! / 2!2!

Favorable Outcomes: Take the 2 P's as 1 unit. We have to arrange 8 units (7 letters and 1 unit of 2 P's) = 8!/2! * 2!/2! = 8!/2!

The required probability = 8!2!/(9!/2!2!)=29**Option D**