Screen appearance changed for unknown reason

Your help appreciated --I must have done something to make this happen but now when I select a passage by dragging the mouse, the selected area is shown only in thin white stripes above and below each stereo track – see attachment – rather than coloring the whole surface of each track. Obviously I inadvertently altered some setting or other. Any help appreciated – thanks! (Mac OS 10.14.6. Audacity 2.3.3)
Screen Shot 2020-05-04 at 7.49.55 PM.jpg

You have selected the Multi-tool in the Tools Toolbar. Select the Selection Tool instead.

– Bill

Yup, that did it – thanks a lot!