Answer
b or FM radio station is 4th.
Work Step by Step
The FM radio station emits radiation of 93.1 MHz or 93.1 x 10^6 Hz compared to the compared to the radiation emitted by the AM radio station (680kHz or 680 x 10^3 Hz). When the frequency decreases, the wavelength increase. Since the FM radio has a larger frequency than the AM radio, it will have a smaller wavelength than the AM radio. Thus, FM radio is placed 4 on the list.
