Whales are threatened by a variety of human activities off the West Coast of the United States，including fishing，ship traffic，and pollution.They have bad effects on whale populations，but are rarely addressed by current whale-protection policies in California，according to a study from the University of California，Davis.
The study，published for open access this week in the journal Marine Policy，examines the main causes of death for nine whale species in the California Current Ecosystem，which stretches from British Columbia，Canada to Baja California，Mexico.The whales considered in the study include gray，blue，fin，minke，North Pacific right，and killer whales.
"We find that it is people that
deem fishing causes whale death，" said co-leading author Eliza Oldach. "But a number of human activities have made the modern ocean a really tough environment for whales to survive.We're excited about efforts that look broadly to rebuild healthy oceans."
The report found that main contributors to whale death are currently，targeted with relevant policy responses：noise，water quality and marine （海洋的） rubbish.But three other threats-nutritional stress，disease and predation （捕食） -need to also be considered to provide a more whole approach toward managing whale deaths.
"Gray whales migrate （遷徙） over 5，000 miles between their breeding grounds at either end of the California Current，" said co-leading author Helen Killeen. "Throughout their journey，they must pass through a large number of human activities，fighting with changes to their environment caused by climate change."
The study comes as the California Ocean Protection Council （COPC） aims to develop a plan for achieving zero death for whales in the California Current Ecosystem this year.Achieving such a goal requires understanding the key drivers of whale deaths and opportunities for policy change，the report said.
（1）Which activity will lead to whales' death？
D
D
A．Going fishing with your friends in a river.
B．Playing with your friends beside the sea.
C．Going sailing with your family on weekends.
D．Throwing rubbish in the sea as you are playing.
（2）What's meaning of the underlined word "
deem" in Paragraph 3？
C
C
A．Catch.
B．Complain.
C．Think.
D．Describe.
（3）What can we learn from Helen's words？
B
B
A．Gray whales are fond of travelling.
B．Gray whales' migration is full of danger.
C．Human being is the only killer of whales.
D．Whales' death is mainly caused by climate.
（4）What should COPC do prevent whales' death？
C
C
A．Get rid of the present policy.
B．Plant more trees along the sea.
C．Know what actually leads to it.
D．Find a right place for them to live.
