In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.

Q: Article: Many people have wondered what makes the oceans rise and fall on the word's beaches twice a day. Those tides are caused by the force of the Moon's gravity and the rotation of the Earth. Gravity acts on the center of any solid object. The Earth is mostly molten rock, but compared to the oceans, we can think of it as a solid object. As you know, the oceans are fluid and lie on the surface of the Earth. When the Moon is overhead, the oceans are four thousand miles closer to the Moon than the Earth's center is. Because the oceans are closer, the Moon pulls harder on the water than on the Earth. This stronger pull makes the water bunch up a little under the Moon, creating a high tide. At the same time, the oceans on the opposite side of the Earth are four thousand miles farther from the Moon than the Earth's center is. The Moon's pull on this water is weak. This water bunches up because it is "left behind"(making another high tide) as the Earth is pulled slightly towards the Moon. When the waters bunch up on these two sides of the Earth, they draw water away from the other sides of the Earth, which creates the low tides. As the Earth rotates, different parts of the land and oceans pass through the high-tide and low-tide zones. And that makes the waters on our coasts go up and down.
Answer: Moon's gravity or Earth rotation

A: According to the passage, there would be no tides if there were no _ .
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Q: Article: Our first winter in Canada was the happiest we have experienced. We were living in the countryside then and had just arrived from Hong Kong that autumn. One evening in mid December snow began to fall. When we looked out of the window and saw that it was snowing, we all cheered. It was the first snow we had ever seen and we were excited. We could hardly wait for the snow to stop so that we could go out to play. Next morning when we woke up, it was still snowing. We switched on the radio and learned that more than ten inches of snow had falled during the night and that since the roads were blocked there would be no school that day. We jumped up and down for joy and begged mother to let us go outside to play in the snow. She said we could go out after breakfast if we dressed ourselves warmly and promised to come back as soon as we felt cold. When we went out, the snow had almost stopped. The roads , paths, gardens, and playing grounds were all hidden under a white blanket of soft snow. It was the most beautiful sight we had ever seen. Just then, we saw some neighbour's children coming out to play. We ran over to join them. Together we built a snowman and a snow house. After that, we took turns sliding down a hill on a large piece of cardboard. We were having so much fun when supper time came. Mother almost had to force us to go in and eat.
Answer: it was the first time they had seen snow

A: The children all cheered when they saw the snow because _ .
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Q: Article: Today, whether or not you follow the latest trends, one's fashion and choice of dress is a reflection of one's individual style and tastes. Can you still remember how you dressed at the start of China's opening-up? Today's program is one of a special series commemorating the 30th anniversary of reform and opening-up in China. In these two episodes we focused on fashion and style and were honored to invite two special guests to join us in studio--Ms. Zhang Ling from Raffles-BICT Inter-national College and Alex from Esquire magazine. When we talk about fashion, color is absolutely crucial. A color can reflect the mood of an individual person or the spiritual temperament of entire society or age. Mrs. Zhang and Alex talked about the colors which have left the greatest impression on them. In the 1960s and 70s, blue and grey were the dominant colors at the time and people had limited choices to dress up. But fast forward to the present, you will find no difficulty in choosing from array of vivid colors in the market. We also gave our guests a list of keywords--traditional brands, jeans, DIY, international brands, personal dress for them to choose from in order to represent the fashion of their generation. We find out that for every keyword our guest chose, there was a special story behind it. Some of the stories brought us back to old times--we even brought some vintage clothing from the 60s and 70s up on stage and invited some audience members to try them on. When we mention fashion, we must mention brand. With increasing disposable income and purchasing power of the Chinese, many luxury brands have flocked into China. However, you could imagine in 1980s, when the first inter-national brand came to China, it unveiled a fashion storm among the Chinese.
Answer: the 1970s

A:
China's opening-up dates back to _ .
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