It can be inferred from the passage that
refraction would be most likely to cause
errors in measurements of a mountain’s
elevation under which of the following
A. When there are local variations in sea
B. When light passes through humid air
C. When theodolites are used relatively far
from the mountain peak.
D. When weather balloons indicate low air
temperature and pressure.
E. When sea level has been carried in to
Within five to twelve miles of the summit.
I’d pick C.
To reduce refraction errors, the
Chinese team carried in sea level to
(35) within five to twelve miles of Everest’s
summit, decreasing the amount of air
that light passed through on its way to
Closer to the mountain -> smaller errors.
Farther from the mountain -> bigger error.
Also, I think B is not right because it is not the humid air per se that could spoil the measurements, but rather many
‘layers of different temperature and pressure’.