The key is the phrase "cross-country", because it means that you're
trying to get somewhere. If you want to stay up the longest time, then
answer c) would be the best one of the 3 given. But if you want to
cover a course in the shortest time, then a) is the best answer.

-John

wrote:
80) What is the approximate proper airspeed to use when flying between
thermals on a cross-country flight against a headwind?

a) The best lift/drag speed increased by one-half the estimated wind
velocity.
b) The minimum sink speed increased by one-half the estimated wind
velocity.
c) The best lift/drag speed with no regard to wind velocity.

The SAA safety site gives the correct answer as "A". I have alway
heard that when flying between clouds you did not consider the wind in
your calculations. Maybe the tricky part of this question is the word
"Thermals".