角膜表面形成的泪膜由3层组成，内层来源于（）
A.泪腺组织的分泌
B.睑板腺的分泌
C.结膜杯状细胞的分泌
D.副泪腺组织的分泌
E.泪腺及睑板腺的分泌
参考答案：C
解析：内层为黏液层，由结膜杯状细胞分泌；极少部分来自泪腺，自内向外分为3层：黏液层、水样层和脂质层。脂质层主要由睑板腺分泌形成，水液层主要由泪腺、副泪腺分泌形成。黏蛋白层主要由结膜杯状细胞分泌形成。
  One night I went to Himeji, a city not far from Kobe. As I walked with my family along the river I saw a __20__. It was a young man who looked just like me. He was wearing a cap and smiling. Around his neck was a leather strap （皮带）and in his hands was a saxophone. He was __21___ the saxophone to his __22__ and just about to play. My family walked on up the river towards the castle __23__ I stayed there by the statue, __24__ of playing a saxophone on TV. Two weeks later it was my birthday. Imagine my __25___ when I opened my present from my parents and found that it was a __26__! I put it to my lips to play, but it wouldn’t make a sound. Then Dad told me to read the __27___ book to find out what to do. After about 15 minutes the saxophone was ready to play. I __28__hard but I couldn’t get the saxophone to play. I was almost __29___ when suddenly the saxophone made the most beautiful sound – loud and clear like I __30__ the music of the man by the river in Kobe.
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