84.　 Because they are so important, ecosystems try to be very careful with these ______(有价值的) resources.

83.　 If the new species is too strong or uses too much of the resources in the habitat, some of the _____(原始的) species may become endangered.

82.　 Professor Stevenson, who has _____ (奉献)himself to protecting the milu deer, gave a talk to Chinese college students in Beijing.

81.　 Many of the world’s animals and plants are in d______.

80.　 Even small things can make a big d________ .

79.　 When the habitat of a species is changed or destroyed, the animal or plant has to either a_____to the change or find a new home.

78.　 If we know more about what causes endangerment, we may be able to take m_______ before it is too late.

77.　 Steve Jones is an __________ (经验丰富的)expert who tries to keep animals and plants from becoming endangered.

76.　 They are ________　 (接见) Michael for the job.

75.　 The students o___ the rules and agree not to use their phones in the classroom.