<prompt> Which stage among the following has maximum contribution in sleep time of an adult?REMNREM 1NREM 2NREM 3  <response>: In adults, the largest amount of sleep time is spent in stage 2 NREM sleep about 60 ; REM phases constitute 20-25 of total sleep time Stages 3 and 4 NREM about 15-20, Stage 1 non-REM about 5. 