题干
After Anna had _______ unusual talk with her teacher, she felt cheerful and made up her mind to work very hard during the rest time of her junior life.
A：a
B：an
C：the
D：\
答案(点此获取答案解析）
B
，那么小球在通过圆周最高点时绳的拉力大小为（空气阻力忽略不计）