Answer:
4 (D): twice the voltage, and the same current will flow through each.
Step-by-step explanation:
When we have batteries in series in a circuit, the equivalent voltage will be the sum of their voltages, and the current flowing through then will be the same.
These batteries are identical, so they have the same voltage, therefore when they are put in series, the equivalent voltage will be twice the voltage of one battery.
So the correct option is 4 (D): twice the voltage, and the same current will flow through each.