题目

One of the most popular American singers of the twentieth century was Elvis Presley. He made the rock ”n” roll music popular all over the world, He sold millions of records and made many successful films, and he helped change the direction of popular music in the 1960s.Elvis Presley was born in a poor family in 1935, His parents were simple country people who often took him to church, where he learned to sing, and he never forgot the kind of songs that he used to sing in church as a child.When he was young, Elvis moved from Toledo to Memphis in Tennessee, where he attended high school, but一单摆做小角度摆动，其振动图象如图，以下说法正确的是（　　）A．t1时刻摆球速度为零，悬线对它的拉力最小B．t2时刻摆球速度为零，悬线对它的拉力最小C．t3时刻摆球速度为零，悬线对它的拉力最大D．t4时刻摆球速度最大，悬线对它的拉力最大