Final answer:
A Program Increment is a planning increment that lasts around 8-12 weeks and involves multiple Agile teams working together to deliver a set of features and functionality.
Step-by-step explanation:
A Program Increment (PI) in the context of the Agile Release Train (ART) or Solution Train is c) A planning increment. It is a timebox for development that typically lasts around 8-12 weeks. During a PI, multiple Agile teams work together to deliver a set of features and functionality to create a potential value-adding increment of the solution.