题干

如图所示,三个完全相同的金属小球a、b、c位于等边三角形的三个顶点上.a和c带正电,b带负电,a所带电量的大小比b的小.已知c受到a和b的静电力的合力可用图中四条有向线段中的一条来表示,它应是(   )

A:F1

B:F2

C:F3

D:F4

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B

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    As a child, I started learning to play the piano, my favorite musical 1 but I was forced to give up when I started my middle school2 I could concentrate more on my studies.

    It's one of my biggest3 to stop practicing the piano when I recall sadly today. During the following years, I kept telling my piano teacher that I would4However, I didn't keep my promise because I was 5 with my study6 I lost touch with my teacher. Some years later, my teacher died. I was very sad because I lost such a good teacher. She was a very warm and gentle person. It hurts me to think she may have been 7 that I never returned. I haven't taken lessons since then but to be honest, I 8 to. Sitting at the piano, I couldn't help recalling many 9 ---times of my practising at home and playing before my teacher and one time my teacher 10 me after I played entire pieces of music wrong in front of her colleagues. I was so 11 that I could hardly say anything. But her 12helped ease my shame. These memories13good or bad, never caused my14 for playing the piano again.

    This thought then led me to think that 15 is like music, and that we all try to play different 16 in the instrument of our life. Sometimes the pitch (音高) is17when we play it well, but sometimes we are out of tone. However, we all continue to create our own 18style of music. No matter what style our music is, it is 19 that we sing the songs of joy, quietness and love. Though I may never make it back to piano lessons, it doesn't 20 that I've stopped making music.