On June 30，2021，Chinese explorer Zhai Mo set sail from Shanghai.The man wanted to live out one of his lifelong dream；circling the Arctic Ocean（北冰洋）.Over the next 503 days，he （1）t

ravelled

ravelled

more than 28，000 nautical miles（海里）.Finally，on November 15，Zhai safely returned to Shanghai in his sailboat.He received a hero's welcome.The 54-year-old had become the world's first man to successfully sail around the Arctic Ocean without（2）

stopping

stopping

（stop）.
   When Zhai first set off，he planned to finish his journey in only four months.But unexpectedly，because of floating ice and strong cyclones（氣旋），the sailor had to repeatedly change his plans.Also，Zhai was forced to leave a certain area during the ice-melting period.If he had failed to do this，his boat would have gotten frozen.And he would have become dinner （3）

for

for

polar bears.Therefore，many people call the sailing route that circles the Arctic Ocean the "the route of（4）d

eath

eath

."
   Luckily，Zhai was（5）

fully

fully

（full） prepared for his journey.He carried enough food and was also able to sail past three of the world's four largest fishing ground.By doing this，he was able to （6）a

dd

dd

some fish to his menu.
   According to Zhai，just a few years ago，it was （7）i

mpossible

mpossible

for human beings to sail around the Arctic Ocean.Because of global warming，however，the ice in the Arctic is quickly melting in recent years.The sailor hopes his historic journey will call the world's （8）a

ttention

ttention

to the influence that human activities are having on the environment.
   For the time being，Zhai plans to stay in Shanghai for a while.But he has already set his next goal：circling around Antarctica（南極洲）.It will be （9）a

bigger

bigger

（big） challenge than before，but the sailor has no fear. "Every difficult journey makes me a （10）s

tronger

tronger

man，" he said. "I'm interested in testing out the limits of my ability."