Which is NOT an input to the Create WBS process?

WBS dictionary is not an input for Create WBS Process while the rest are ...

WBS dictionary is the output of create WBS process, so my answer to your question is "WBS dictionary"..

WBS Dictionary, as rest all are inputs, this is only a repository of terms and definitions and cannot be treated as a input.

WBS Dictionary will not be a direct Input, however it can be used as reference.

WBS Dictionary

WBS dictionary is output

WBS dictionary is one of the output of create WBS process

WBS dictionary is one of the elements of the Scope Baseline therefore it is not an input, it is an output of the Create WBS process.

The Scope Baseline include:

1. Project Scope Statement

2. WBS

3. WBS dictionary

Fourth option 

WBS Dictionary

The use of Work Break Down Structure (WBS) is bring down or breaking objects at atomic level and / or Managing Levels.

1) Project Scope Statement: This is used for breaking down scope.

2) Organizational Process Assets: In organisations the process tools, templates and key level documents which can be break down according to the project requirements.

3) Scope Management Plan: This is used to break down the scope at simple statement levels.

4) WBS Dictionary: This is a type of Glossary and /or Dictionary where concepts are already broke at atomic level. 

Conclusion: WBS Dictionary is a subset of Work Break Down Structure (WBS) hence this can't  be an input for WBS rest of all can be an Input.

Project Scope Management Plan is not an input to the WBS Creation process