On a winter afternoon, I was walking in a garden in the warm sunshine. I felt warm and ________ .

Suddenly, an apple tree caught my eye. I walked ________ towards it, searching for a perfect apple. However, the apples were red and big. I couldn’t wait to pick one. It was the   ________ in my eyes. In order to enjoy it, I took a little bite, but bitterness (苦涩) quickly spread through my mouth. At this moment, I realized that beautiful ________ didn’t mean the beauty inside and that the beauty inside was much more important than the outside, I walked to the dustbin and prepared to throw it away. After much hesitation (犹豫), I ________ throwing it away. I thought I chose it and I should eat it up though it was really ________ to eat. I must be responsible for my ________.

After eating it up, I tamed round to the apple tree, ________ that since the beautiful apples didn’t taste good, the ugly one must be delicious. When I got ready to pick the apple which I was not happy with, I doubted whether it was delicious. Then a boy rushed out behind me and picked the apple. I saw him eating the apple. I knew that it must be very delicious for his big ________. I lost a delicious apple because of my hesitation.

Life is like picking apples. When we decide to do something, we should begin without any hesitation or we may ________ the chance.

The Mayan number system appeared in the fourth century, which was about 1,000 years earlier than the time when the European number system was created. It is different from the Arabic number system with a base 10. The Mayan system had a base 20. This system is believed to have been used because the Mayans lived in such a warm area and there was hardly a need to wear shoes, 20 was the total number of fingers and toes, so the system was workable. Therefore, there were two important numbers in this system. Besides 20, the other important number is 5, which had a connection with the number of fingers and toes on one hand or foot.

The Mayan system used two symbols（符号）. A dot （.）was used to mean the units（one to four）and a dash（—）meant five. The Mayans were also the first to create symbols of nothing（or zero）. The most common symbol was that of a shell（）but there were several other symbols（e.g. ahead）. It is interesting to learn that with all of the great experts on Maths and scientists in ancient Greece and Rome, it was the Mayan Indians who came up with this symbol zero or nothing. Picture 1 is a form of different numbers and how they would have been written.

From further study, people found that the 360 day calendar（日历）also came from the Mayan. They actually used base 18 when they made the calendar. Each month included 20 days with 18 months in a year. This left five days at the end of the year which was month in itself, full of danger and bad luck. In this way, the Mayans had invented the 365 day calendar.

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There are many famous inventors and scientists in history. You must have heard about a lot of them and know them well. But you may not know Nikola Tesla.

Nikola Tesla and his inventions are well known to people in the area of science and electricity, but not quite known to the general public today. Nikola Tesla was a Serbian-born inventor, who later moved to the US. He is most well-known for his inventions in the area of electricity and electrical engineering. He is considered one of the greatest electrical engineers in history.

Why was Nikola Tesla not appreciated while others in his time became so famous to the public? Some say Nikola Tesla failed to make the right business decisions. Others say it was because of his, “mad scientist” qualities(特质)—the same qualities that helped him come up with some of his best ideas. His qualities worked against him, leading him to many strange ideas. Towards his last years, he played with many ideas that seemed unacceptable to the public at that time. He worked very hard on them, which made people think he was mad.

Many of Tesla’s inventions and patents didn’t end up being used in the exact way he had planned for them. Some of those include his high-frequency lighting ideas, wireless power and the free energy receiver.

If you are interested in green energy and reducing your electricity bill, check out products that are based on Tesla’s work. They help create green energy at home, without relying on the electricity companies and without paying them. They save people money through producing electricity at home, based on Nikola Tesla’s inventions.

Tesla has too many inventions, and more than 250 patents are under his name. However, he never really made a lot of money out of them. He had a bigger dream: to provide free energy for all.

Nikola Tesla is not alone. There are many other inventors in history that invented many useful things but are not known to the public…

Thomas Edison was born in America in 1847. As we all know, Edison was a famous inventor. His most famous invention is the electric light bulb. H    46    , before he really invented it, he failed more than one thousand and five hundred times. N    47     knew when he would succeed, but he never gave up. Instead, he tried and tried. In order to save time, his b    48     and hands seldom rested. Finally when the light of a bulb lasted for 45 hours, he r    49     that he succeeded. It became one of the most p    50     tools in the world. That is a great gift for human beings.