In a Solenoid Magnet in Which the Wires Are Wound

Multiple Choice

In a solenoid magnet in which the wires are wound such that each winding touches the previous,which of the following will increase the magnetic field inside the magnet?

A) making the winding radius smaller
B) increasing the wire radius
C) increasing the radius of the solenoid
D) decreasing the wire radius
E) immersion of the solenoid in gasoline