1     moment I stepped out of school, I saw a dark blue­gray cloud approaching. But I didn’t know what a huge tornado was. I heard my mother yell my name. She asked me to get in her car. I ran to the car and got in. She     2     (immediate) started the car and headed for our house.

When I looked back at the cloud, it had a small funnel­looking (漏斗状的) cloud inside. We finally got to our house and then we heard a loud siren (警笛). My dad looked scared in the     3     (emergent). He brought the radio and a flashlight, while my mom    4     (grab) some batteries. My mom attempted     5     (shelter) me from the disaster. We turned on the radio and heard that an EF­2 tornado had touched down just east of my school. Then I heard a long deep sound that began to shake the house. That was the most horrible moment of my life and I hoped nothing like that     6     (occur) again.

A sandstorm,     1     originated in Mongolia on Tuesday, swept through vast regions of northern China, causing heavy pollution. The storm, according to the National Meteorological Center, was the     2    (strong) in China so far this year and affected several provincial-level regions. It was said that strong winds     3    (blow) over loose sand and soil created the conditions for sand and dust storms. Satellite images showed that by Wednesday morning, it     4    (cover) 854,000 square kilometers,     5    (rough) twice the size of the US state of California.     6    violent sandstorm swallowed everything in its path and caused much inconvenience. Visibility remained lower than 1,000 meters in some parts of northern China. The     7    (government) of the affected areas urged people with respiratory(呼吸道)illnesses to avoid outdoor activities and recommended that brightly colored clothes     8    (wear)to avoid accidents amid poor visibility. The capital’s parks stopped boats and cable cars     9    (ensure)the safety of visitors. It is hard to say     10     there will be more such weather conditions, but the NMC will keep close watch this spring.

The red-crowned crane is known as one of the     1    (large) crane species worldwide, reaching an     2    (impress) height of approximately 150 cm. The crane has white feathers that are as pure as snow, with some black feathers on its face, neck, and wings. But what makes it really special is the bright red skin on top of its head,     3     gives it its name.

This magnificent species can be found inhabiting various regions,     4    (include) China, Russia, Mongolia, Japan, and the Korean Peninsula. In China, during the warmer months, the red-crowned crane resides in rivers and wetlands     5    (locate) in the northeastern parts of the country. As the temperature     6    (drop), these cranes migrate to the east-central regions of China.

The red-crowned crane’s diet primarily consists     7     fish, snails, and aquatic plants. It skillfully captures its prey, displaying its agility and adaptability in aquatic habitats.

In Chinese culture, the red-crowned crane holds great symbolic significance. It     8    (see) as a representation of long life and good luck. The graceful presence of this crane in folklore and traditional art highlights its esteemed status as a symbol of prosperity and vitality.

To witness the red-crowned crane in flight or observe its elegant courtship displays is     9    (true) a remarkable experience. This remarkable bird’s stature, beauty, and cultural significance make it a cherished species, beloved by nature enthusiasts and those     10     appreciate the wonders of the world.

We usually see baby ducks paddle in     1     straight line behind their mother in a pond. That ducks swim in a row is such a common phenomenon that it’s become an idiomatic expression. Many studies have looked at why ducklings do this.

    2     turns out that the baby ducks ride on their mom’s waves to save energy. For a long time, scientists didn’t understand why swimming in this pattern helps baby ducks save energy. A team of scientists in Scotland and China set out     3     (find) the answer. Its findings     4     (publish) earlier this year reveals ducklings save energy by staying in line behind their mother, where they can ride the waves created in her wake.

Zhiming Yuan, a naval architect, worked on the study. He made a     5     (create) computer simulation of duck waves and studied the simulation. He found when a duckling swims     6     its own, it kicks up waves causing wave drag, which makes it much     7     (hard) for the duckling swimming. However, to our     8     (amaze), when ducklings swim in their mother’s wake, the wake drag is reversed. The baby duck feels a push instead of a drag. And when ducklings line up     9     (neat) behind their mom, they share with each other. Each duckling in the line     10    (pass) its waves along to the ones behind it. So, ducks swim in a row.