Text Highlight Tool Won't Turn Off

When I turn on the text highlight tool to highlight text in an adobe pdf, I can't turn the tool off after I finish using it. The only way to turn it off is to select another tool or to close the document. If you select another tool it stays on also until you select another tool or close the document. I have tried to click on the tool, right click on the tool and everything I can think of and it just won't turn off after your turn in on. What am I missing?