一道中学英语选择题，急需帮忙，，谢谢～～～～
The students spent as much time as they could ______ their lesson.
A.to practise B.practising c.practise D.be practiced
希望大家告诉我答案，并且一定要告诉我原因，谢谢了
参考答案:B
spend time doing sth 花时间做...
as much time as they could 是完整的一个词组，表示尽可能多的时间