Control key function not working on Comments/Annotations

I used to be able to use the "control" key to highlight specific blocks of text to perform a certain annotation function on (such as strikethrough), but it all of a sudden stopped working.  Thus, if I have say 3 rows of text, it only selects all three rows instead of just the text in one row that I want to make the annotation to.

I have Acrobat version 11.0.23 and am using Windows 10

This is rather urgent, so if anyone can help, I'd really appreciate it.