It took humans thousands of years to understand our own planet, and centuries _______ our neighboring planets. Nowadays, new worlds are being _______ every week.

Up to the present time, astronomers have _______ more than 370 “exoplanets”—planets orbiting (绕……运动) outer space stars (恒星) other than our sun. There is a “hot Saturn (土星)” 260 light-years from Earth that orbits its parent star so _______ that a year there lasts less than three days. _______ another star 150 light-years out is a burning “hot Jupiter (木星),” where upper atmosphere (大气层) is being burning to form a huge comet-like tail. Astronomers have found another three _______ orbiting a pulsar (脉冲星)—the remains of a once huge star shrinking (收缩) into a small atomic nucleus the _______ of a city. Some planets have obviously fallen into their suns. Others have been thrown out of their _______ to become “floaters” that float in the darkness of the universe.

Among all these, scientists are eager to find a clue of the _______: planets like the Earth. That is, planets orbiting their stars at just the right distance—neither too hot nor too cold—to ________ life as we know it. We have not yet found planets that are quite like our own, ________ because they’re inconspicuous (不起眼的). To see a planet as ________ and slim as ours among the brightness of its star is like trying to see a firefly in a fireworks display.   ________ by pushing technology to the ________, astronomers are rapidly approaching the day when they can find another Earth. And when they do, they can examine it for ________ of life.

We always think that it’s ok for us to leave our plants unattended during our vacation as we believe that they’ll survive just_______ .Plus, plants won’t scream like pets, so_______ must be okay, right?

A recent study_______ by a group of scientists at the Tel Aviv University has discovered that some plants will scream_______ a high frequency when they are_______ stress. The research was_______ on tomato plants and tobacco plants by cutting their stems and_______ them of water. A microphone is placed 10cm away from the setup.

When they started cutting the_______, they found out that the plants started“_______” between 20 and 100 kilohertz and they believe that this scream is__________meant to warn other plants and__________ nearby. When the tomato plant’s stem was cut, 25 ultrasonic (超声波的) distress (痛苦) sounds were__________ over the course of an hour, and on the other hand, 15 ultrasonic distress sounds were recorded from the tobacco plant.

__________they deprived the plants of water, the tomato plants recorded even __________ distress sounds with 35 distress sounds in a hour__________ the tobacco plants recorded about 11 distress sounds.

The plants also responded differently__________ different kinds of stress,__________, the tobacco plant gave out a more intense “scream” when they were deprived of water than when their stems were cut. But plants that were in no __________ danger released less than one ultrasonic sound per hour.

The group of scientist then said that this changes the way we think of plants as we had always__________that they are silent, but the thing is their voices are so high-pitched that we just can’t bear them. Last year, another study has found out that plants feel pain when touched and it will, __________, cause the release of a disgusting chemical.

There are often many assumptions made about young people aged 15 to 21, but only a few can be proved with hard evidence. Now, new research has been published to help people get a better idea of these _________ young people.

According to an international survey in 2016, young people in emerging (新兴的) economies like China and India have a _________sense of hope about the future, compared with those living in Europe, North America and Australia.

The survey was _________ between September and October by the Varkey Foundation, a UK-based non-profit organization. It surveyed 20,000 young people who were born between 1995 to 2001 in 20 countries. They were asked questions about their hopes, ambitions, personal views and community values.

It was found that 53 percent of those questioned in China thought the world was becoming a better place – the highest percentage among the countries surveyed. Some 93 percent of them also felt _________ for the future because of advances in technology, such as in medicine, renewable energy and computing.

Indian youth were the second most_________, with 49 percent taking a positive view of the world’s prospects.

_________, young people in France, Italy and Turkey had the most negative outlook on the future, with fears about extremism and the rise of global terrorism.

“At a time of nationalist and populist (民粹主义的) movements (such as Brexit (脱欧) or US President Donald Trump’s plans to build a wall along the US border) that focus on the _________between people, the evidence shows that young people share a _________ similar view of the world,” Vikas Pota, chief executive of the Varkey Foundation, told The Guardian.

“They are a generation that is deeply _________ about the future of the world,” he added.

As for young people in China, what they __________ most is the impact of climate change — some 82 percent of those who responded to the__________ said so.

Pota said it was __________ that young people in China were aware how serious the problem of climate change is.

“This is surely a hopeful development. The young population of China is more aware than anyone of the seriousness of the climate crisis – and will be__________ for change,” he told South China Morning Post.

The overall survey showed a sense of optimism in the __________ and opinions of the generation that is likely to shape the next few decades, according to Pota.

“They are more likely to travel, to migrate across borders and to forge (建立) friendships in other countries than any __________ generation,” he said. “Global citizenship is not dead. It could just be getting started.”