Identify which of the following is a primary source and which is a secondary source.
A book written by a historian about World War II and a diary written by a soldier during World War II
The diary is a primary source and the book is a secondary source.
Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Identify which of the following is a primary source and which is a secondary source.

### Response:
The diary is a primary source and the book is a secondary source.