What does the "O" line represent on the chart? What is indicated by a sharp spike below the “O” line?

A sharp spike below the 0 line means to go further than you think you need to go

Explanation: this is what google said

the answer to fill in the blank in this question would be the word resource, it is defined as the money, material or people (since human resource is a very valuable good) that a company or a person has at disposition (meaning they can use the resource as they see fit), to be able to complete a task or achieve a goal.