The electrical charge of 70 millivolts (mV) can be converted to volts (V) by remembering that 1 volt equals 1000 millivolts. Therefore, to convert millivolts to volts, you divide the number of millivolts by 1000.
So, if we take 70 mV and divide it by 1000, we get:
70 mV = 70 / 1000 = 0.07 V
From the options provided, the correct answer is 0.07 volts (option b).