0 A Collection of TOEFL Reading Comprehension 01

          All mammals feed their young. Beluga whale mothers, for example, nurse their calves for some twenty months, until they are about to give birth again and their young are able to find their own food. The behavior of feeding of the young is built into the reproductive Line   system. It is a nonelective part of parental care and the defining feature of a mammal, the (5)      most important thing that mammals-- whether marsupials, platypuses, spiny anteaters, or placental mammals -- have in common.           But not...