$4.$ We can use statistical process control $($SPC$)$ chart

need for a SPC Change $+$ standard deviation $+$ The sample mean $(\stackrel{}{x})$

B$.$ Standard deviation $+$ Upper Control Limit $($UCL$)+$ Lower Control Limit $($LCL$)$

C$.$ The sample mean $(\stackrel{}{x})+$ Upper Control Limit $($UCL$)+$ Lower Control Limit $($LCL$)$

D$.$ Range $+$ standard deviation $+$ Upper Control Limit $($UCL$)+$ Lower Control Limit $($LCL$)$