After being "rubbed", an object has acquired a charge of -1 nanoCoulomb. Choose the statement that is true (only 1):
A. 6.25 x 10-9 protons have been rubbed off the object.
B. Electrons have been transferred to the object.
C. The object must be made out of conducting material.
D. The object must be made out of insulating material.
E. The object is a semiconductor.