That is an interesting question, but I'm almost 100% sure it was F sharp.
If you'll locate where there are 3 black keys together, it is the white key that is just after the first black key.
The key that uses all black keys on the piano is the key of D minor.
The middle black key in the set of three black keys
A#/Bb
if you have a piano then press a black key. it also depends on the key you are pressing too, as different keys make different sounds.
To play G on the piano, locate the black key to the right of the white key G. Press down on the black key to produce the sound of G.
There are 36 black piano keys that are raised and further back than the white keys. The black key on the right of a white key is a sharp and the one on the left of the white key is a flat.
To play an A on the piano, locate the black key to the right of the A key and press it down with your finger. This key is also known as Bb.
Eb is the black key on the right of the groups of two black keys.
There are 7 octaves on a standard grand piano (plus a minor third, or one additional "black key"). If each octave has 5 accidentals (or black keys) then 7 octaves would have 35 black keys, plus the additional B Flat at the bottom of the piano.....so: A 72 key piano has 36 black keys.
Ab is the middle black key in group of three black keys on the piano.
To play D flat on the piano, locate the black key immediately to the left of the white key D. This black key is D flat. Press it with your finger to produce the sound.