Which of the following is required for all valid lambda expressions?
B.
The lambda expression s -> true is valid, making Options A, C, and D incorrect.
Parentheses () are not required on the left-hand side if there is only one variable.
Brackets {} are not required if the right-hand side is a single expression.
Parameter data types are only required if the data type for at least one parameter is specified, otherwise none are required.
The remaining choice, the arrow operator ->, is required for all lambda expressions, making Option B the correct answer.