The inner (dot) product of two non zero vectors \[\overrightarrow {\text{P}} \] and \[\overrightarrow {\text{Q}} \] is zero. The angle (degrees) between the two vectors is A. 0 B. 30 C. 90 D. 120

The correct answer is $\boxed{\text{C}}$.

The dot product of two vectors is defined as follows:

$$\overrightarrow {\text{P}} \cdot \overrightarrow {\text{Q}} = |\overrightarrow {\text{P}}| |\overrightarrow {\text{Q}}| \cos \theta$$

where $\theta$ is the angle between the two vectors.

If the dot product is zero, then $\cos \theta = 0$. This means that the angle between the two vectors is either $90^\circ$ or $270^\circ$. However, since the vectors are non-zero, they cannot be parallel, so the angle must be $90^\circ$.