Based on the clue 'because they fit one inside the other russian matr...', what is the answer?

Based on the clue 'because they are never found in chemical compounds...', what is the answer? Based on the clue 'because they cant digest cellulose pandas may eat ...', what is the answer? Based on the clue 'because they develop from a single ovum this varie...', what is the answer? Based on the clue 'because they excrete fluid outside the body sweat ...', what is the answer? Based on the clue 'because they have this quality cats claws dont get...', what is the answer? Based on the clue 'because they often prodded cattle with sticks cowb...', what is the answer? Based on the clue 'because they squeeze their prey to death boas pyt...', what is the answer? Based on the clue 'because they were too inexperienced or low in rank...', what is the answer?