图示为某一皮带传动装置。主动轮的半径为r1，从动轮的半径为r2。已知主动轮做顺时针转动，转速为n，转动过程中皮带不打滑。下列说法正确的是 。（填入选项前的字母，有填错的不得分）
A．从动轮做顺时针转动
B．从动轮做逆时针转动
C．从动轮的转速为
n
D．从动轮的转速为
n
BC
题目分析：由于皮带交叉，主动轮做顺时针转动，则从动轮做逆时针转动，故B正确；由于转动过程中皮带不打滑，即二者边缘线速度相同v主=v从，由v=ωr及ω=2πn知：v=2πnr，从动轮的转速为
n，故C正确．
Scientists, doctors and mental health professionals have been studying the connection between colors and mood for years. Many now believe that colors can not only bring about emotional reactions, but can also correct mood. Colors behave in three basic ways: active, passive and neutral (中和的). Active colors are warm colors, including yellow, orange and red. These colors bring confidence. Warm colors can also bring cheerful attitudes. Yellows and golden colors work well in offices, kitchens and study areas. Reds heat up a room. Passive colors or cool colors make people calm, quiet and satisfied. Bedrooms, private areas and bathrooms are great places for blues and greens. Beige, gray and white are thought of as neutral colors. They help to put the focus on other colors or serve to tone down colors that might otherwise be overpowering on their own. You can easily change the look or feel of a room by making good use of different colors. Mixing and matching colors is an excellent way to balance color and emotion, and provide a welcoming feel for guests. To create a feeling of warmth and comfort in a room, use bright, warm colors like yellow, orange and red. These colors are good choices for rooms that appear cool due to limited sunlight. Yellow adds cheerfulness to dull rooms. You can add yellows to rooms which are not closely related to happy thoughts, such as kitchens and laundry room. In rooms where there's plenty of sunshine, cool colors can provide a calming environment. Sage greens and sky blues are perfect for bedrooms, playrooms and activity areas. Neutral colors, such as pale gray, white and beige, send a peaceful message to your brain. It's not a coincidence that most doctor's offices, coffee shops and mental health centers are decorated in neutrals. To make your wall color choices better, pick out furniture that will provide a visual contrast. Cool colors make a room seem larger than it is and warm colors make rooms feel smaller. Title: The 小题1: ____________ between colors and mood
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