Is this right?

I’ve been studying using the exam tool and came across the question and answer below. I thought efficiency was increased by pulling more heat out out of the combustion process which would DECREASE temperature of flue gas. Am I wrong?

Question: High-efficiency gas furnaces improve heating efficiency by _____

answer: increasing air flow and the temperature of flue-gas exhaust

You are correct. Very strange answer. Multiple choice? Trick question?

Here is the whole question

High-efficiency gas furnaces improve heating efficiency by ______________.

increasing blower speed and evaporating flue gases
decreasing air flow and the temperature of flue-gas exhaust
reducing air flow across the heat exchanger
reducing the temperature rise and condensing flue gases
increasing air flow and the temperature of flue-gas exhaust

From Practice for State Licensing Exam (if your state requires it) - InterNACHI http://www.nachi.org/practice.htm?start=420&show=30#ixzz2YILvRKxz

reducing the temperature rise and condensing flue gases

To me the above is the best answer of the group and it is poorly worded???

Agreed Charley and something I am sure Ben would correct!

Thanks guys.

Darren