Option-V doesn't make a checkmark!

Help! I have several spreadsheets where I use a checkmark as the data. I create the checkmark by typing "Option-V" on my Mac. But today, suddenly the checkmark doesn't work! When I typed "option-v", I got this character instead:

ˇ

Then, when I tried to do something else, the "Control-V" combo makes the √ that I wanted. Why has this changed? I haven't changed any settings and can't figure this out. I need the √ to go back to the "Option-V" key combo because "Control-V" has different uses in other applications. I just can't figure out why it changed or how to put it back!

Does anyone know what's going on? This is across the board on every app I've tried. Caps-lock is not on. No function keys. And the Option keys and the "V" seem to be operating properly for other uses. I just can't use it to make the checkmark, and I can't use "option-v" in every application.

ˇˇˇˇˇˇˇˇˇˇ This is not what I want!

I need this:√√√√√√√√√

Help!