Red Manufacturing work with around 40 different suppliers.

Explanation

The correct answer is 'arms length'. This is a tactical purchase (as it is low value) and keeping the supplier at arms-length means that Red Manufacturing could possibly exploit them to reduce their prices (think back to the Kraljic matrix and where Blue Business would likely fall). A Partnership or Single- Source relationship requires investment into the relationship, and as the products are low value and Red Manufacturing have a lot of other suppliers, they should not be investing time in developing that relationship with Blue Business. An adversarial relationship wouldn't be advantageous as it may lower the performance of the supplier. See the relationship spectrum on p.5 - this is a hot topic for the exam