Which of the following would cause an iron bar to start generating a magnetic field

I am not sure the answer is c

the reason is because the moon has some form of gravity, and that gravity pulls the ocean tides.

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.