The "safe key" is the computer version of what you're doing and then it's separated by what's called a "pipe" character ( | ). You can get that by holding down shift and then hitting the backslash, which is the \ character. Then after the pipe will be what your customer will see.
So if you want to list out Yes, No and Not Sure as options it would be:
The only limitations with the "Safe key" on the left of the pipe is that it has be all alphanumeric characters (just letters and numbers) and they have to be in lowercase. And spaces can't be used. That's why "Not Sure" looks like it does in the example above.
If you have more trouble with webforms our Support Team is happy to help via a ticket.