Recently, I was looking for something online, or probably browsing aimlessly, when I happened on a name I hadn’t thought of since I was a child: Alfred P. Morgan. Someone had uploaded a digitized version of The Boy Electrician. I was instantly swept back more than half a century to my local library. In my mind I saw the familiar metal shelving and the blue-gray binding of my favorite book, also written – and illustrated – by Morgan: The Boys’ First Book of Radio and Electronics.

Which of the following expressions is a synonym for ‘aimlessly’ on the first line of the text?