E6D07 (B)
What is the usable frequency range of inductors that use toroidal cores, assuming a correct selection of core material for the frequency being used?
A. From a few kHz to no more than 30 MHz
B. From less than 20 Hz to approximately 300 MHz
C. From approximately 10 Hz to no more than 3000 kHz
D. From about 100 kHz to at least 1000 GHz
