Final answer:
In legal terms, "shall" is used to indicate a mandatory requirement, while "may" indicates an optional or discretionary action. Option 1 correctly defines these terms as used in American legal English.
Step-by-step explanation:
In American legal English, which has historical roots from England, certain terminology has specific meanings. The term "shall" represents a mandatory requirement. It is an imperative, binding, and unconditional term, making it a command rather than a suggestion. In contrast, the word "may" suggests an optional or discretionary action, indicating that there is a choice or permission involved. Thus, the best definitions from the options provided are: 1) Shall means a mandatory requirement, while may means an optional requirement. This use of shall and may is consistent in legal contexts, providing clarity and precision essential for legal documents and proceedings.