Listen to the statement and circle the appropriate letter. From the passage, we can conclude that when the number of sea otter rises, the number of sea urchins will __________ .

A．sea urchins
B．sea otters
C．the relationship of many sea living creatures in the kelp forest

A．Because the study range is wider.
B．Because the current equipment is more advanced.
C．Because of the devotion of the ocean explorers.
D．Because of the use of multi-disciplinary approach.
E．Because of people’s rising concern about the ocean exploration