某同学做“验证力的平行四边形定则”的实验情况如图甲所示，其中A为固定橡皮条的图钉，O为橡皮条与细绳的结点，OB和OC为细绳，图乙是在白纸上根据实验结果画出的图．

连续阴雨时，生活在土壤中的蚯蚓会爬出洞穴，此现象与生物哪一因素有关？（  ）

将盛有等质量、等质量分数的稀盐酸的两只烧杯，放在托盘天平的左右两盘，天平平衡．在左盘烧杯中加入10克碳酸钙，恰好完全反应，若要使天平重新平衡，则右盘烧杯中应加入的物质可能是（　　）

阅读理解

　　William Jefferson Clinton(威廉·杰斐逊·克林顿)was born in a small town of America. He was born on 19th August, 1946. He was president of the USA from 1993 to 2001.

　　Wang Fei is a teacher. He was born in Shanghai and he teaches in a middle school. He is very friendly to his students. He lives in a big room with a TV, a kitchen, a bedroom and a bathroom. He is very young but very nice.