白细胞分化抗原是指A．B细胞表面膜分子B．T细胞表面膜分子C．即_爱下问搜题

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问题单项选择题

白细胞分化抗原是指

A．B细胞表面膜分子
B．T细胞表面膜分子
C．即指CD
D．白细胞表面的所有膜分子、
E．免疫细胞在分化、成熟及活化过程中表达的膜分子

答案

参考答案：E

解析：白细胞分化抗原是不同谱系白细胞在正常分化成熟的不同阶段及活化过程中，出现或消失的细胞表面标志。

明成祖派遣郑和下西洋的目的是

A．为扩大明朝的海外影响

B．为促进明朝海外贸易的发展

C．为购买国内没有的珠宝、香料

D．为加强同海外各国的联系

完形填空

The leaves（树叶） fluttered（飘动）over Josh’s head. The park near his home had always been one of Josh’s 36 places. He liked to watch the colors of the trees glow（闪耀）in the sunlight, 37 the golden trees. It was the same color as his trumpet（小号）. He smiled when he 38 the music the leaves made. Josh sat down and looked at his watch. His father would meet him in a few 39 for their first practice in the park.
Josh and his family lived in an apartment building.When Josh first began playing the trumpet, he 40 in his own living room. Then the family next door had a new baby. To avoid 41 the baby, Josh would 42 his practice time in the park. His father told him it would be good to practice in a wide, open 43 like the park. The baby next door would be able to sleep 44 , but Josh was not very happy with the 45 . He enjoyed visiting the park, but he didn’t want to practice there. He was 46 that he would embarrass（使……难堪）himself in a pubic place if he played the wrong notes（音符）. He didn’t want people to 47 him as he played in the middle of the park.
Josh’s father was a great trumpet player, who once played in a jazz band. He couldn’t possibly understand how 48 it would be to practice in the park！
His father came over and 49 Josh’s daydream(遐想). “Josh, are you ready to practice?” He sat down and 50 his own trumpet from its case. He held the trumpet to his 51 and began to play. The beautiful music floated into the blue afternoon sky.
Josh looked up at the golden trees. The leaves 52 to be dancing to the tune his father was playing. Josh felt 53 as he watched the people walking by and smiling at his father.
He 54 to play like that. Josh put his trumpet to his mouth and blew. He had such a great time that he didn’t 55 if he played a few bad notes. Now he and his neighbors could all be happy.

A．preparation

B．description

C．arrangement

D．appointment

A．embarrassing

B．interesting

C．encouraging

D．disappointing

B．interrupted