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130. Desert mammals also depart from the normal mammalian practice of maintaining a  constant body temperature. Instead of trying to keep down the body temperature deep inside the body, which would involve the expenditure of water and energy, desert mammals  allow their temperatures to rise to what would normally be fever height, and temperatures  as high as 46 degrees Celsius have been measured in Grant's gazelles.  The word "maintaining" is closest in meaning to which of following?