I want to know the answer to the following question:
What is the simplest case of an ISP using an upstream ISP?
All the background I'm provided with is that "In the simplest case, a single connection is established to an upstream ISP and is used to transmit data to or from areas of the Internet beyond the home network; this mode of interconnection is often cascaded multiple times until reaching a tier 1 carrier.". Is that enough to answer the question?
Answer: yes