shall VS will！ 大侠请进！

Opening with tributes to jazz-age divas like Bessie Smith and closing with Koko Taylor's electrified gravel-and-thunder songs, the program will trace theblues' vigorous matriarchal line over more than 50 years.

A.  program will trace

B.  program shall trace

答案：B

我想请教一下will 和shall在用法上有什么区别，具体到这一题上为什么选择shall?

谢谢！