问题
单项选择题
在肌细胞兴奋-收缩耦联过程中起媒介作用的离子是
A．Na+
B．Cl-
C．K+
D．Ca2+
答案
参考答案：D
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在肌细胞兴奋-收缩耦联过程中起媒介作用的离子是
A．Na+
B．Cl-
C．K+
D．Ca2+
参考答案：D
There once was a farmer who lost his watch in his barn（谷仓）. The watch was very cheap but it was very 1 to him because it was a gift from his father. After 2 the barn for a long time, he gave up and asked for 3 from a group of children playing nearby. He 4 them that the person who found the watch would be rewarded（报偿）. Hearing this, the children hurried inside the barn 5 . They searched everywhere but still could not find the 6 . Just when the farmer was going to give up, a little boy went up to him and asked to be given another 7 . The farmer looked at him and thought, “Why not? After all, this kid looks honest.” So the farmer 8 the little boy back into the barn. After a while the little boy came out with the watch in his hand! The surprised farmer asked the boy how he 9__ where others had failed. The boy replied, “I did nothing but sit quietly and listen for the sound of the watch.” This shows us that sometimes a 10 mind can think better than an excited one.
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