Answer:
B. 3,4 Volt
Explanation:
Here we need to use Ohm's Law, because we have electric current, voltage and resistances. This law state:

So, first we need to calculate the total resistance to then find the voltage. The resistances can be placed in two ways: in parallel, in series.
The pair 4 and 8 ohms are parallel, so we solve:


Which is,

Now, this total resistance of parallels ones is placed in series with the 3 ohm resistance, in this case we just sum, because they are in series:

Now that we have the total resistance of the circuit, we use the Ohm's Law:

Therefore, the right answer is B.