I think you mean D is answer.mundasingh123 wrote: Farther distance from the peak means more layers of air (with different temperature and pressure or same temperature and pressure ) ? we need to clarify this.When its already mentioned that refraction takes place due to temperature and pressure change , we know that humid air means temperature and pressure change .This makes use of info given in passage itself and no outside knowledge , does it?
But i think the case is which is more right
Both C and D are right.Even B is not incorrect.
but i think C is more right
see this line as well
Line 33-38 from the passage
To reduce refraction errors, the Chinese team carried in sea level to within five to twelve miles of Everest's
summit, decreasing the amount of air that light passed through on its way to their theodolites
As per D measuring was done through ballon,we can still attack it.
So,C is more clear and less controversial than D so i think C wins