[单选题]
Faraday's law of induction state+ bfcyogl65z1tj 4t0ws)4q;0 /w:d ys-trd sso.; sxp6uas)m hze jel9 that the $emf$ induced in a loop of wire is proportional to
A. the magnetic flux.
B. the magnetic flux density times the loop's area.
C. the time variation of the magnetic flux.
D. current divided by time.
