骨骼肌纤维兴奋-收缩耦联的耦联因子是

A．Na⁺

B．K⁺

C．Mg²⁺

D．Ca²⁺

E．Cl^-

There are many kinds of friends. Some are always (1) you, but don’t understand you. Some say only a few words to you, but understand you. Many people will step in your life, but only (2) friends leave footprints.
I shall always recall the autumn and the girl with the (3) . She will always bring back the friendship between us. I know she will always be my best friend.
It was the golden season. I could see the yellow leaves (4) with the cool (5) . In such a season, I liked walking alone on the roads covered with leaves, (6) to the sound of them.
Autumn is a (7) season and life is uninteresting. The free days always get me (8) . But one day, the sound of a violin (9) into my ears like a stream flowing in the mountains. I was so surprised that I jumped to see what it was. A young girl, standing in the wind, was (10) in playing her violin.
I had (11) seen her before. The music was so nice that I listened quietly. Lost in the music, I didn’t know that I had been (12) there for so long but my existence did not seem to disturb her.
Leaves were still falling. Every day she played the violin at the comer of the building (13) I went downstairs to watch her performance. I was the only listener. The autumn seemed no longer lonely and life became (14) . (15) we didn’t know each other, I thought we were already good friends. I believe she also loved me.
Autumn was nearly over. One day, when I was listening carefully, the sound suddenly (16) . To my astonishment, the girl came over to me.
"You must like music from the violin." she said.
"Yes. And you play very well. Why did you stop’." I asked.
Suddenly, a (17) expression appeared on her face and I could feel something unusual.
"I came here to see my grandmother, but now I must leave. I once played very badly. It was your listening every day that (18) me. " she said.
"In fact, it was your playing (19) gave me a meaningful autumn," I answered, " Let’s be friends. "
The girl smiled, and so did I. I never heard her play again in my life. I no longer went downstairs to listen to her. Only thick leaves were left behind. But I will always remember the fine figure of the girl. She is like a (20) —so short, so bright, like a shooting star giving off so much light that makes the autumn beautiful.

Ⅱ. 完形填空/Close

A．flowed

B．grew

C．entered

D．ran