Expertshavefoundthatnormalsleepcanbedividedintofive______stages
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Althoughtheyagreethatlifeisimportantandshouldberespected,theyfeelthatthequalityoflifeshouldnot__(ignore).
Manyothernewtechniquesarenowavailablethatenablemoreresearch___(do)inthetesttubetoseeifchemicalsproduceharmfulbiologicaleffects.