The correct answer is: C. 2 IB
The current I1 flowing through R1 and R2 should be equal to or greater than 2 IB for good stabilization in voltage divider bias. This is because the current through R1 and R2 sets the voltage at the base of the transistor, and if this voltage is too low, the transistor will not be able to properly amplify the signal.
Option A is incorrect because 10 IB is too high. If the current through R1 and R2 is too high, the voltage at the base of the transistor will be too high, and the transistor will be saturated. This will cause the transistor to not be able to properly amplify the signal.
Option B is incorrect because 3 IB is too low. If the current through R1 and R2 is too low, the voltage at the base of the transistor will be too low, and the transistor will not be able to properly amplify the signal.
Option D is incorrect because 4 IB is too high. If the current through R1 and R2 is too high, the voltage at the base of the transistor will be too high, and the transistor will be saturated. This will cause the transistor to not be able to properly amplify the signal.