算法的空间复杂度指的是什么？如何表示？

A)A work plan.
B)Business management.
C)Computer skills.
D)A training course.

A)He worked as a volunteer.
B)He attended a summer school.
C)He travelled around the country.
D)He made a survey in a local hospital.

A)He has been writing a paper.
B)He has been studying all night.
C)He has been playing games all night.
D)He has been working on the night shift.