Answer the questions on the basis of the information given
f1 (x) === x for 0 is less than or equal to x is less than or equal to 1
= 1 for x is greater than or equal to 1
= 0 Otherwise
f2 (x) = f1 (- x) For all x
f3 (x) = -f2 ( x) For all x
f4 (x) = f3 (- x) For all x
Which of the following is necessarily true?