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阅读短文，从方框中选择合适的句子填入文中空缺处，使短文完整、通顺April 20Dear Liz,Thailand is wonderful. Life in Bangkok is busy and interesting. My host family lives in a nice and quiet town outside the city. There are Mr and Mrs Phairat, their son Sanan and their daughter Chinda in the family.I go to an international (国际的) school with Sanan and Chinda. I'm good at the spoken language, but Thai writing is very difficult. The cooking class is my favorite. When I come back, I will cook you a real Thai meal.Last weekend I went to Pattaya Beach with Sanan an如右图所示，小明分别用甲、乙两个滑轮把同一袋沙子从地面提到二楼，用甲滑轮所做的总功为W1，机械效率为η1；用乙滑轮所做的总功为W2，机械效率为η2。若不计绳重与摩擦，则 A. W1 = W2，η1 =η2        B. W1 = W2，η1 <η2 C. W1 < W2，η1 >η2        D. W1 > W2，η1 <η2