30. (A)Flexible. 　　(B)Critical. 　　(C)Supportive. 　　(D)Cautious.

52. 　　We can learn from the first paragraph that ________. 　　(A)human activities have changed the way turtles survive 　　(B)efforts have been made to protect turtles from dying out 　　(C)government bureaucracy has contributed to turtles’ extinction 　　(D)marine biologists are looking for the secret of turtles’ reproduction