The answer of this question can be achievied by applying Kirchoff's first law. This law states that the sum of all the currents entering a junction must be equal to the sum of all the currents that are exiting. We can write the equation in the following manner
Thus, in our current problem, we can write the following equation (we'll use the convention of negative signs for entering currents, and positive signs for leaving currents).
So, by isolating A we find
Alternative B) 2A