Adevice used to open and close an electric circuit is a(n)
a. light bulb.
b. energy source.
c. switch.
d. resistor.
select the best answer from the choices provided

What type of electromagnetic wave is used in security pens? a. x-rays c. microwaves b. visible light d. ultraviolet radiation select the best answer from the choices provided

The star betelgeuse is about 600 light-years away. if it explodes tonight, a. we'll know because debris from the explosion will rain down on us from space.b. we'll know it immediately because it will be brighter than the full moon in the sky.c. we won't know about it until 600 years from now.d. none of the above.

The substances that are necessary for producing of certain hormones and that store and transport vitamins