按学习的载体分，学习可以分为（）。
A.试误式学习与顿悟式学习
B.个别学习与小组学习
C.书本学习与项目学习
D.机械学习与有意义学习
参考答案：C
She walked home by herself at night, _____ she knew that it was dangerous.
A．once
B．as
C．unless
D．although
The continuous rain ______ the harvesting of the wheat crop by two weeks.
A．set back.
B．set off
C．set out
D．set aside
