An e.m.f. of `100` millivolts is induced in a coil when the current in another nearby coil becomes `10` ampere from zero in `0.1` second. The coefficient of mutual induction between the two coils will be
A. 1 millihenry
B. 10 millihenry
C. 100 millihenry
D. 1000 millihenry