Comprehension Problem

My teacher recently gave me a English comprehension... there's one question i don't know how to answer it...
The passage is really long, so i only posted the part of the passage which is related to the question:

"That afternoon we passed a mace-shaped marker of black steel, which showed that we had entered the great desert of Tenere. An hour later, when the wind had already begun to thrash itself out, we saw our first salt caravan. There were 100 camels in two coiling silver strings like centipedes. Three men came dashing towards us across the sand. They asked for nothing but to shake hands. I understood their need for human contact in this dreadful void. At sunset we......."

-adapted from Michael Asher, 'Impossible Journy', Penguin Books Ltd

The question was:
'I understood their need for human contact in this dreadful void.'
Explain in your own words what the writer means by this statement, by paying particular attention to the words in italics.

I understood the passage well, but, i don't really know how to put my answer into the question... i don't know how to explain myself. Anyone could teach me the techniques to answer such questions?