15. An ohmic resistor is placed across the terminals of two different batteries, one at a time. When the resistor is connected to battery A, the resulting current is three times the current when it is attached to B. What can you say about the battery voltages:

(a) ΔVA = 3·ΔVB,

(b) ΔVA = ΔVB,

(c) ΔVB = 3·ΔVA, or

(d) none of the preceding?