最近美国宇航局公布了开普勒探测器最新发现的一个奇特的行星系统，命名为“开普勒-11行星系统”，该系统拥有6颗由岩石和气体构成的行星围绕一颗叫做“kepler-11”的类太阳恒星运行。经观测，其中被称为“kepler-11b”的行星与“kepler-11”之间的距离是地日距离的
，“kepler-11”的质量是太阳质量的
倍，则“kepler-11b”的公转周期和地球公转周期的比值是：（ ）
A．
B．
C．
D．
答案：C
题目分析：根据万有引力提供向心力
可得公转周期
，设太阳距离为M，地日距离为r，则有“kepler-11b”的公转周期
，对比各选项可知C正确。
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| I have a good friend. 1 name is Lisa. She comes from the US. Now she and her family 2 in Shanghai. She likes many 3 here in China, especially (尤其是) Chinese food. "Chinese food is really 4 ", she says. "It's different( 不同的) from the 5 in the US." In America, she often 6 bread, French fries and salad. But in China, she can eat 7 of different food. Lisa says. "Chinese food is so delicious. It's nice and 8 . Eating is very 9 here. I 10 Chinese food." | |||
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