原题
录音 1
What function do sea otters perform in their marine ecosystem?
AThey keep kelp forests healthy by preying on sea urchins.
BThey remove clams and other invasive shellfish from shorelines.
CThey are food for predators such as whales and seals.
DThey build shelters that act as a buffer against storm damage.
正确答案：A
解题思路
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