短文填空（10个小题，每小题1分，共10分）
阅读短文，用方框内所给单词的正确形式填空，使短文意思通顺、完整。请将答案写在短文后相应题号的横线上。注意：①每个词只能用一次。②每空限填一词，有些词需要做相应的变化。③其中有两个多余选项。

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Life is not easy as a Junior 3 student. You have the ______ of study and exams. From time to time, you may feel depressed. If that ______, you have to take measures to fight it. Eating salt might help you_______up, scientists have found.
While too much salt can lead to high blood pressure and heart disease, not enough can cause depression, a study has reported.
Researchers at the University of Lowa in the US did study. They found that without enough salt in their bodies, rats don’t do things they normally ______ , like drinking sweet water.
Salt is a_____ anti-depressant( 抗抑郁剂), researchers say.
Health experts recommend an adult take about six grams of salt a day. A gram of salt is about the _____of a toothpaste cap.
Humans have a long history of salt eating. In the Stone Age, people didn’t need to find salt, because they hunted most of their food, and ate a lot of red meat. Red meat has _______of salt. But when people began to farm, _____ about 10,000 BC, they started to eat_________of grain and much less meat. They had to find another way to get salt. ______ time went by, salt became a seasoning( 调味料).