Nikola tesla used rotating magnetic fields to generate, transmit, and use ac (alternating current). today alternating current has replaced direct current in most situations. what is the advantage of using ac power over dc power? a) it is safer to use than dc power. b) it can be used directly in all appliances. c) its current can be raised or lowered easily by a transformer. d) its voltage can be raised or lowered easily by a transformer. eliminate

AC voltage can be raised or lowered easily by a transformer. (D)

A).  AC is not necessarily any safer than DC.

B).  The only reason most appliances run directly on AC, and few run on DC, is because AC has been so widespread for so long that THAT's what everybody has coming out of the outlets in their house, and so THAT's the way manufacturers BUILD the appliances.  If they BUILT appliances to run on DC, they would only sell a few, to people who spend a lot of time traveling in their mobile campers, but not to anybody who needs appliances for their home.

C).  The current that flows INTO a transformer depends on how much current is being taken OUT of it, and the current being taken OUT of it depends on the voltage at the output, and on how many people have how many things connected to the output of the transformer.

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.