My ans is MAC of halothane is lesser than methoxyflurane

 

After ruling out other options I left with
5) An increase in ventilation rate makes the onset of anesthesia more rapid for either agent.

As, solubility = potency= 1/MAC
Less soluble= rapid induction and recovery time
All thanes are cardiodepressent.

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Will go with no. 2.
Oil:gas coefficient reverses to give lipid solubility?

 

Here is my silly little way;
Gas anathetic with high B:G ratio are more soluble in the blood/lipids, so the they are not readily available as "free" in the CNS to induce the anesthesia. As they are soluble, tissues would provide a prolonged supply for these gas to get into CNS, prolonging the anesthesia, i.e. the higher the B:G ratio, the slower the gas both in iduction and recovery. But for the gas to get into the CNS, it must first be "solublized" in the blood, and this is done by increasing its conc. in the alveoli ( MAC ). So, an agents with low B:G ratio would have higher MAC and so less potent ( because we have needed more dose to reach the same ED 50). Putting all these thought together:
B:G:
NO = 0.5
Halothane = 2.4
methoxyflurane = 13, then
Blood solubility ( and so rapidity ) : NO < halo. < methoxy., then
MAC ( and so potency ) : NO > halo. > Methoxy.
***
Halo and methoxy do not act faster than NO so A is incorrect.
MAC of halo. is not less than that of methoxy. so B is obviously incorrect.
The only inhaled anathetic that does not produce cardiodepression is NO so C is wrong.
Recovery from methoxy. is by far slower than that of halo. D is incorrect.
And we left with E, which I have strong feeling that its the right answer but I dont know exactly why!