In a capital budgeting context, what is meant by perfectly correlated periodic cash flows and under what

Question:

In a context, what is meant by perfectly correlated periodic cash flows and under what conditions might they be expected to occur?
Capital Budgeting
Capital budgeting is a practice or method of analyzing investment decisions in capital expenditure, which is incurred at a point of time but benefits are yielded in future usually after one year or more, and incurred to obtain or improve the...