Which of the following statements are true? (select all that apply.) a. all moving electric charges give rise to electromagnetic waves. b. at any time, the electric and magnetic field lines are parallel to each other. c. the intensity of the wave drops off as 1/r. d. electromagnetic waves can exert forces on charged particles that they encounter. e. the direction of can be found using the right-hand rule. f. put your four fingers along , sweep them in the direction of and your thumb will point along .