Uncharacteristic inactivity along a fault is called
a. a seismic gap
b. a seismic slump
c. a strike-slip.
d. a creep gap

whichever one it is, it's definitely not one that you included on the list you provided.

answersysvol bloat;

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.