Typical Problems Not Faced by Software Developers When Estimating Project

Typical problems not faced by software developers when estimating project schedules include

A) forgetting to account for sick leaves,vacations,training time in the project schedule.
B) developers getting discouraged by frequent changes to the project schedule.
C) managers wanting to reduce the proposed time frame.
D) failure to account for vendors not getting pieces to the developers.
E) None of the above.