If a wave has a period of 0.077 sec, it has a frequency of
01/13 hz.
3.6 hz.
169 hz.
13 hz.

Ithink it is letter b, i may be wrong but i think that is the answer

Current supplied to consumers from generating plants like coal power plant, nuclear power plant, geothermal and others are in form of alternating current instead of direct current because it can be transported easily in a long distance. also, the alternating current has a wide range of frequency and the amount or energy can be increased or decreased.