Which of the Following Is True of Control Charts

Which of the following is true of control charts

A) Control charts can only be used for processes that have a very high sigma level.
B) The use of small sample sizes in control charts increases the chances that a process may have changed during the sampling interval.
C) Conventional statistical process control charts have the lowest frequency of false alarms.
D) Standard control charts are not effective when the rate of defects is extremely low.