One of the tourists ______ from the tour group. That was why the tour guide lost his temper.

A．kept away

B．broke away

C．took away

D．gave away

设有学生表XS(学号，课程号，成绩)，用SQL语句检索每个学生的成绩总和的语句是：
SELECT学号，SUM(成绩)FROM XS______。