Before a tester begins the process of exploratory testing, what tool should he have in place to give him an idea of what to explore in the systems and what kinds of things to look for?

Q: Before a tester begins the process of exploratory testing, what tool should he have in place to give him an idea of what to explore in the systems and what kinds of things to look for?

a) A Roadmap

b) A Bug List

c) A Defect Document

d) A Charter