To answer this question, we need to understand the different types of methods in a class.
Option A) a sub procedure - This option is incorrect. A sub procedure is a type of method that performs a specific task within a class, but it does not return a value.
Option B) a function - This option is incorrect. A function is also a type of method that performs a specific task within a class, but it does return a value.
Option C) an event - This option is incorrect. An event is not a type of method, but rather a mechanism that allows objects to communicate with each other.
Option D) Both a and b - This option is correct. A method in a class can be both a sub procedure and a function, depending on whether it returns a value or not.
Option E) All of the above - This option is incorrect. While option D is correct, option E includes option C, which is incorrect.
Therefore, the correct answer is option D. A method in a class can be both a sub procedure and a function.