I'm getting ready to install this thermostat in my daughters house for her but I've got a question about the wiring. The furnace is gas/forced air and old thermostat is mercury with only TWO wires (1 red and 1 white). That's it just those two wires, nothing else. No air cleaners or A/C connected just an old furnace in an old house and trying to save her some money with the programmable thermostat.
The installation guide shows 5 wire connections [O/B Y R - G W]. Is it a safe assumption that the red and white simply get connected to the R & W terminals? Excuse my ignorance and fear but I just don't want to damage the furnace control board by connecting the new thermostat incorrectly.
_____Thank you in advance for any and all advice (sorry I don't know the make of the furnace at this time but can find out if needed).

You are absolutely correct. Simply hook Red to R, and white to W. Make sure to kill the power to the furnace before messing with any wires. Make the simple swap out and turn power back on. Only other thing I would suggest would be to read the complete t-stat install instruction booklet for any thermostat set-up or programming.

You are absolutely correct. Simply hook Red to R, and white to W. Make sure to kill the power to the furnace before ~ ~ ~ ~ ~ t set-up or programming.
I thank you very much, as I stated I know it sounded stupid but I just didn't want to make any assumptions and damage anything in the process. Again Thank You from myself, my daughter and grandchildren!

You are welcome. Happy New Year.