Answer:
A. False, if you use notes from the key the piece is written in, your descant will definitely fit.
Step-by-step explanation:
It is generally best to use notes that belong to the key of the piece when composing a descant. This will help ensure that the descant fits harmonically with the rest of the music. Using notes that do not belong to the key can lead to dissonances and clashes with the underlying harmonies. However, it is possible to use non-diatonic notes in a descant as long as they are used tastefully and with consideration for their impact on the overall sound of the music. So the correct answer is A.