When does sign-extension occur? Select one: a. When a smaller signed integer data type is converted into a larger signed integer data type b. When a larger signed integer data type is converted into a smaller signed integer data type c. When a smaller unsigned integer data type is converted into a larger unsigned integer data type O O d. When a smaller unsigned integer data type is converted into a smaller unsigned integer data type e. When a smaller unsigned integer data type is converted into a larger signed integer data type