Read the text below and decide which answer (A, B, C, D or E) best fits in the gap. Geological deposits of salt were formed millions of years ago when what is now land, lay under the sea. It is hard to believe that salt is now such a cheap commodity because centuries ago, it was the commercial equivalent of today’s oil. The men who mined salt became wealthy and despite the risks, a job in the salt mine was highly coveted.
Nowadays, the specific microclimates in disused mines have been exploited for the treatment of patients with respiratory illnesses. The silent, dark surroundings in a mine are considered ______in encouraging patients to relax.