To dynamically change a reference line using parameter action, you first create a reference parameter. Next, add a parameter action for it. Finally, .a. add a reference line whose value follows a reference parameter. b. add the sheet you want to control as the bottom-right element in the layout. c. also add a URL action that points to the dashboard itself. d. add a reference line with a per pane scope and a tooltip.

a. add a reference line whose value follows a reference parameter

Explanation:

To dynamically change a reference line using parameter action, you first create a reference parameter. Next, add a parameter action for it. Finally, "add a reference line whose value follows a reference parameter."

This is because to dynamically change a reference line using parameter action, one needs to do the following:

1. Attribute the reference line with a parameter

2. Utilize a parameter action to make the parameter interactive.

3. As your users interact with the view, the reference lines automatically update to deliver more context to the data.

i will say b. laboratory technician   and if wrong then sorry