Your 1099-R should have the distribution code listed on the form. The code(s) in Box 7 of your 1099-R helps identify the type of distribution you received. These codes with your answers determine if your 1099-R income is taxable or not.
If your form does not have this code, please contact your Financial Institution who issued the 1099-R for the correct code.
See TurboTax FAQ - What do all the codes in Box 7 of the 1099-R mean?