IMO, the best way is to do it like Calc and Excel : a single click on the row number. The people are used to the Calc or Excel way, and it’s the effortlesser.
And what is also important, is the possibility to select multiple rows. To see if as in Calc or Excel, when you click on another line number, it deselects the previous selected line. From my point of view yes, because it’s a quick way to deselected everything we had selected.
In this case it is also necessary to implement the CTRL+Click to be able to select several whole lines.
CTRL+click or not, you also have to implement SHIFT+click on the line number, to be able to select in one click the part between what is already selected and what you add with SHIFT+Click.