As in most multi-choice questions, you need to sort out the nonsense first to eliminate one possible answer straight away. In a 3 or 4 choice question, one answer is always totally wrong, one may be almost right and you then need a degree in English comprehension to sort out the nuances of the other two. With experience, anyone with a broad knowledge of a subject, plus sound English comprehension and good reasoning can pass a multi-choice exam on a similar subject with little or no specific study. That is why systems knowledge seems to be declining , but I digress with my rant...
In a 2 choice question it is easier to arrive at what what they want. In the above, answer 1. is nonsense, because even if you did climb into warmer air, fogging would not be much of an issue. For air to be warmer above, you would be looking at an inversion situation and that would only be for a short part of any climb. In any case, in a type of aircraft likely to have windscreen heat you probably don't need to see outside to climb, only to land. So answer 2 is your only choice.
Bird impact protection is a major reason for windscreen heat on many transport types. The impact protection function of heat is evidenced by speed restrictions when it is unserviceable.
The prevention of ice formation or fogging is certainly a descent issue, but could be taken care of with external bleed air or alcohol spray etc and in some older types that's how it is done.
Fortunately the descent fogging answer was not offered, or depending on how it was worded, you could have had a difficult choice. The exam would then need to provide a 'both 2 & 3' type of answer (statistically it could probably be shown that whenever you get a 'both 2 & 3' choice, it is the correct answer on 90% of occasions).
Last edited by Mach E Avelli; 12th Jan 2010 at 07:59.