What Is the Difference Between Formal Rulemaking and Informal Rulemaking

What is the difference between formal rulemaking and informal rulemaking?

A) Formal requires notice while the latter are simply immaterial changes to rules.
B) Formal requires a public comment period and informal rulemaking does not.
C) Formal requires public hearings and informal does not.
D) Formal requires Government in the Sunshine notices and informal does not.
E) none of the above