What is not the cash flow timing conventions used in DCF?
选项：

A:A cash outlay to be incurred at the beginning of an investment project occurs in year 0.;
B:A cash outlay, saving or inflow which occurs during the course of a time period is assumed to occur all at once at the end of the time period.;
C:A cash outlay to be incurred at the end of an investment project occurs in year 0.;
D:A cash outlay or receipt that occurs at the beginning of a time period is taken to occur at the end of the time period.