Unlike electric field lines, magnetic field lines are continuous and always form closed loops.
a. true
b. false

True

Explanation:

Magnetic field refers  to a region around a magnetic material or magnet, where a magnetic effect i felt. The magnetic lines of force are continuous lines that always travels from north to south pole and forms a closed loop. It is for these reason that magnetic poles exists as dipoles and not mono-poles. Electric field lines however travel from positive to negative and cannot return to the positive hence they do not form closed  loops, They can only travel in just one direction.

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.