Select Points by String
Click on the required string and all the points in that string will be selected.
If the SHIFT or CTRL keys are held down when the string is clicked, the existing points will
stay selected, and the string points will also be selected.
Remember that you are really selecting Points not Strings.
Menu: Points/ Select/ by String
Select Centre Pts
Tick this box to also select any centre points used on curves in the string.