Rearrange the parts to make a meaningful sentence.

P. nor the teachers knew

Q. neither the principal

R. who had painted

S. the wall outside the library

Explanation

1. 01

   "Neither ... nor" is a pair: Q begins it, and P completes it with the verb "knew".

2. 02

   Knew what? R "who had painted", and "painted" needs an object: S.

3. 03

   So the order is QPRS: "Neither the principal nor the teachers knew who had painted the wall outside the library."