Why does a firm that buys production materials outside need reliable suppliers?

1. A firm buying outside is depending on someone else to keep its line running. 2. Having to shut down production because vital parts were not delivered on time is a costly disaster. 3. That is why firms must consider whether outside sources can supply reliably as well as cheaply. 4. Reliability is not the same as low price, so option A confuses two separate supplier qualities. _Source: OpenStax Introduction to Business (CC BY 4.0), Ch 10 "Achieving World-Class Operations Management", section Make or Buy?_