The answer is:
D. the reading on A1 minus the reading on A3.
The rate at which charge flows through a circuit is known as the current and is measured in amperes (A). Charge does not pile up and start to accumulate at any given point, such that the current at one location is more than at other locations. In a parallel circuit, the charge splits into separate branches and there can be more current in one branch than there is in another. The total amount of current in all the branches when added together is the same as the amount of current at locations outside the branches. The total current is given as.
Itotal = I1 + I2 + I3 + ...In
In the above circuit, Itotal = A1 = A2 + A3
Thus A2 = A1 - A3