Identify the part of speech for the word "but" in each sentence. no one answered the ad but me. () there is but one choice to make in this case. ( ) sadie said she would go but she had to bring her sister. ( )

Here are the answers to the given sentences above:
-No one answered the ad but me. It is used as PREPOSITION.
-There is but one choice to make in this case.  It is used as an ADVERB.
-Sadie said she would go but she had to bring her sister. It is used as a CONJUNCTION.
Hope this helps.