Which of the following is the most common non-behavioral reason for projects being completed behind schedule and going over budget

A) Selecting a wrong person as the project manager.
B) Selecting a wrong person as the sponsor.
C) Accepting a high-risk project.
D) Inadequately defined requirements.

______指在教学中要不断地安排和进行专门的复习，使学生对所学的知识能够牢固地掌握和保存。