Beijing residents woke up to yellow sky on Sunday morning as northern China       1     (hit) by the largest sandstorm of the decade.

Air pollution readings rose to the upper limit of 500 at 8 a.m., according to data from the city's environmental monitory center, as visibility was reduced to     2     (little) than 1,000 meters in parts of the city.

The city's weather bureau advised residents to stay indoors as much as possible, while experts are working to find out     3     the sandstorm came into being.

Smartphones have become an essential part of our daily lives. However,     1     (protect) younger students’ eyesight and make sure they focus on their studies, primary and middle schools will have more specific rules to limit students’ mobile phone use on campus.

The Ministry of Education     2     (release) a notice in January that restricts primary and middle school students from carrying mobile phones to school. Those who still require their phones for some reason must get their parents’ and teachers’ approval and must hand their phones over during class time.

The policy aims to improve students’ focus on study and fight for    3     (addict) to the internet and games.

On March 20, the Sanxingdui Ruins site,     1    (locate) in the Chengdu Plain and famed as "one of the greatest archaeological discoveries of mankind in the 20th century," unveiled more than 500 archaeological discoveries and cultural relics .

“Thanks to the new discoveries, we’ve     2    (basic) figured out the layout of the sacrificial zone of the Sanxingdui site,” said Lei Yu, a researcher at the Sichuan Provincial Cultural Relics and Archaeology Research Institute, who heads the ongoing excavation.

The about 12-square-kilometer site     3    (discover) in 1929, and major breakthroughs were made in 1986 with the discovery of two pits believed to be for sacrificial ceremonies. The pits were accidentally uncovered by local farmers digging up earth to make bricks.

Koshiba had a legendary life. When he was a kid, he dreamed of being a soldier or musician, but his dream was broken when his right hand was damaged by polio(小儿麻痹症).While in the hospital, he read Adlbert Einstein’s books and     1     (become) interested in physics. He never made it to the top of his physics class in high school, but went on to study at the University of Tokyo, then the University of Rochester,     2    he earned his PhD. “There are things in the world you can achieve despite poor academic records.” Koshiba said. What     3     (count) most is adopting an active attitude toward studying.

The virtual choir was the idea of award-winning composer and conductor Eric Whitacre. Born in the USA on 2 January 1970, Whitacre     1    (begin) studying music at the University of Nevada in 1988. He fell in love with Mozart’s classical music when he sang for the university choir.     2    (move) by the music, he said, “It was like seeing color for the first time.” He graduated from university in 1995, and then received a master’s degree in musical composition from the Juilliard School in New York in 1997. over the next 10 years, Whitacre’s original compositions began to become quite popular among choirs     3     singers.

Levi Strauss was the first man to begin producing special, strong trousers for working people. He made these trousers from a fabric called “denim”—a tough fabric     1     probably came from a town named Nimes in France. Many people now think the English word “denim” comes from the     2     (France) words “de Nimes”, which means “from Nimes”. Later, Strauss added special metal buttons to the trousers to make them even     3     (strong) and they immediately became very popular.

China plans to recruit 84,330 college graduates as teachers in rural primary and middle schools in 2021 as part of efforts    1    (promote) rural vitalization, the Ministry of Education said Wednesday.

The recruitment     2    (be) mainly for the once-impoverished areas to consolidate the results of poverty reduction, according to    3    notice issued by the ministries of education and finance on carrying out the rural special-post teacher recruitment program this year.The program is expected to strengthen the teaching capacity of some weak subjects in rural schools    4     arts, foreign languages and information technology, said the notice.

Hawaii is the only state not on the continent of North America. The State of Hawaii consists     1     8 bigger islands and 2000 more small islands. Of the bigger islands, Hawaii Island is not only the largest but also the youngest. People can find a few active volcanoes in the island. Mauna Loa and Kilauea are the most active volcanoes,     2     the American government has opened Volcanoes National Park. The island’s largest city Hino, also the second largest one in Hawaii State,     3     (stand) on the northeast coast of the island.

Are you humorous? People who are humorous can recognize what’s funny in others and can amuse others as well. At home, a sense of humor can brighten family life, so amuse     1     (you) and your family members through jokes if you can. In the classroom, a humorous teacher will not make the students feel     2     (bore) with learning. In hospitals, humor can sometimes help to reduce pain of the patients and enable them to recover     3     (strong). No wonder people often say laughter is the world’s     4     (good) medicine.

I have many goals. The most important one is to travel around the world and I am trying my best to make it come true. The reason is     1     our world is so fantastic that I want to explore it. There are so many different things in the world     2     (experience). While     3     (travel), I can learn different languages and make friends with the local people. I believe I can achieve my dream.