问题
单项选择题
关于激素的代谢下列哪项正确
A．卵巢主要合成雌二醇和雌酮两种雌激素
B．雌酮是雌二醇的降解产物
C．雌三醇由雌酮降解而来
D．卵巢分泌的孕激素主要是孕二醇
E．孕二醇的降解产物是孕酮
答案
参考答案：A
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关于激素的代谢下列哪项正确
A．卵巢主要合成雌二醇和雌酮两种雌激素
B．雌酮是雌二醇的降解产物
C．雌三醇由雌酮降解而来
D．卵巢分泌的孕激素主要是孕二醇
E．孕二醇的降解产物是孕酮
参考答案：A
Listening to an Ipod, playing loud video games and going to see the movies are harmful to your hearing. ___71____ Block(堵住)，walk and turn—that’s what hearing scientists want you to do when you face a loud noise. Block the noise from entering your ears. 72 And turn it down. About 15% of all school-age children live with some hearing loss. And it’s a growing problem. _ 73 Block It Out! 74 It starts at zero. Sounds that are too loud or sounds that last too long can harm the inner ear’s hair cells (细胞)。 Most people don’t know that listening to headphones at full volume(音量) is harmful. So turn down the volume and protect your ears. What’s Too Loud? 75 And 60 decibels is totally safe.
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