When people hear the word “stress”, they usually think of something bad.     1    , stress can have several benefits (益处) for the body and mind. To begin with, people may feel stressed when there     2     something important to do. For example, some students are stressed before a big test. The stress might make them feel nervous, but it also     3     (make) them focused. This type of stress can help people work efficiently (高效地) to meet their     4     (goal). Another way stress benefits us is that it can keep us healthy. Scientists who study stress learnt a little stress can make the immune system strong. When your body learns to respond (反应) to some stress, it’s able to protect you better from     5     (ill). The final way that stress benefits us is that it can help     6     respond to danger. If you see a car coming around the corner too fast, you might experience stress. This stress sends a message     7     (warn) your brain of danger, allowing your body to respond     8     (quick). You may not be able to jump out of the car’s way soon enough     9     the stress. Of course, too much stress is harmful to our bodies and minds. But the right amount of stress makes us more efficient,     10     (health) and safer.

Have you heard about the periodic table ( 元素周期表) lately? Well, there’s some big news about this special table, but first, remember that the periodic table is used to organize all the elements, or things that make u    1     our world.

Elements are all around us. Iron is one of the commonest elements found within the Earth. You probably know the element oxygen. It is the element that we b    2       in all the time. And elements can combine (结合) to make new things l    3     H2O. This is hydrogen and oxygen put together, also known as w    4    ! Learning about these things helps us better understand the world we live in.

But have you ever noticed something missing in the periodic table? There were already 114 elements. But the seventh row of the table was not f    5    , until now! In December, scientists from IUPAC(国际理论与应用化学联合会) found the f    6     elements that were missing. They are elements 113, 115, 117 and 118.

“To scientists, this is of greater v    7       than an Olympic gold medal, ”Ryoji Noyori, a Nobel honored chemist, told the Guardian.

The new elements are heavy metals and were made in l    8    . These kinds of elements can’t be found in nature. Scientists are still looking for ways to use these elements, and other elements in the eighth row, in our daily lives.

Scientists have been working on this for 10 years, but the work is not done. Now they will p    9     to look for “element 119 and beyond”. But for now, be careful when you read your C    10     books because the periodic table might be outdated.