The answer is D: Salt and Water
Answer : The voltage applied by the batteries is, 6.0 V
Solution : Given,
Resistance of flashlight = 2.4 ohm
Current in the circuit = 2.5 Ampere
Formula used :

where,
V = applied voltage
I = current in the circuit
R = resistance of light
Now put all the given values in the above formula, we get

Therefore, the voltage applied by the batteries is, 6.0 V
This is funny, because last year I did a project on wave lengths, but despite that; Violet light has more energy than yellow light because on the light spectrum, violet has the least wavelengths. This means they carry the most energy.