Which One of the Following Statements Are TRUE

Which one of the following statements are TRUE?

A) The progress chart graphically displays the days each employee is on duty.
B) Gantt charts are tools that determine the optimal schedule of jobs in a job shop.
C) Gantt charts only display the ideal use (planned schedules) of resources over time because the actual use is too variable.
D) The machine chart is a visual tool useful for determining the consequence of schedule changes on a trial- and- error basis.