After analyzing the provided code and the possible expressions, the correct answers are those that evaluate to True based on returning the inner function 'g' and the assignments 'a' and 'b'. The expression 'a(2) == 4' is True because 'a' becomes the function 'g', which squares its input (2*2). The expression 'a is not None' is also True because 'a' is assigned a function, not None. Therefore, the expressions 'a(2) == 4' and 'a is not None' are correct.